The boom years of the high-tech industry were good ones for women.

The 10 biggest tech companies based in Silicon Valley added nearly 20,000 women to their work forces. The number of female managers and technical workers grew by nearly 4,000.

And it wasn’t just the luck of the times. Many of these companies were trying to attract women by doing things to help them balance work and family. One result: Five of the 10 earned places on Working Mother magazine’s list of best companies for women to work.

But a Mercury News analysis of federal employment data shows that despite these gains, women fell behind. After five years of stupendous growth in the valley’s 10 highest-grossing tech companies - firms that last year sold a combined $150 billion worth of products and services - women made up only 32 percent of their work forces in 2000, down from 35 percent in 1996.

And the largest proportion of female workers were not managers or engineers, but what they have traditionally been: office workers.

Industry experts point to a number of factors to help explain why the representation of women suffered at the top tech giants based in Silicon Valley, while men, particularly those of Asian descent, increased their share:

-Women left large corporations for start-ups or to launch their own businesses, where they could more quickly rise to the top and work under more flexible schedules.

-The kinds of technical jobs that grew most in the late 1990s were ones for which women had not been groomed in large numbers. Although they earned 56 percent of all bachelor’s degrees in 1998, women accounted for 27 percent of those degrees in computer and information sciences, according to the U.S. Department of Education. That has fallen from its peak in 1985, when women were awarded 37 percent of those degrees.

-Women have few role models within the top ranks of large tech corporations. Even at Palo Alto, Calif.-based Hewlett-Packard - a company recently named one of the Top 10 companies for women by the National Association for Female Executives - men made up nearly 70 percent of its officials and managers in 2000.

‘‘You’re looking at an industry that is very particular to men,’’ said Sarah Sherwood, president of Silicon Valley Women in Business, the local chapter of the National Association for Female Executives. ‘‘Women are leaving the industry because if you don’t have power in an organization and you don’t have a structure that’s understanding of women’s issues, you run into trouble.’’

The reason women choose to join some high-tech firms over others may lie in what programs and perks those companies provide to foster the work-life balance that is important to so many working women.

At Cisco Systems, Chief Executive Officer John Chambers heeded employees’ pleas for convenient child care and built a 65,000-square-foot day care center next to the sprawling campus.

Sun Microsystems offers adoption assistance for families, subsidized day care and a lactation program designed to help balance the nurturing of a new baby with work responsibilities.

Hewlett-Packard pioneered job sharing more than a decade ago, a program that, while not exclusive to women, enables many of them to share a full-time job with a colleague.

After the first of her three children was born 12 years ago, Kristy Ward, a 20-year HP veteran, applied to become one of the first job-share candidates at the company.

‘‘I thought going into it that it would really limit my possibilities for advancement, but it hasn’t,’’ said Ward, 44, of Santa Clara, Calif. After 10 years, her job-share partner retired in 2000 and Ward took a part-time managerial job so she could be home when her children get out of school.

‘‘For me, the benefit has been in the flexibility,’’ she said. ‘‘It makes me able to be more focused when I’m at work than I would be otherwise because I know that I have time for the other things.’’

Radha Basu, of Saratoga, Calif., is an example of how women have used the business acumen they glean at the valley’s largest companies as a springboard for their own ventures.

Basu never thought she would leave HP, where she had worked for 20 years and risen through the ranks to become general manager of the company’s international software division. But in mid-1999, Basu heard about the opportunity to become a CEO at a fledgling company that is now SupportSoft, makers of support automation software.

She was excited about leading a company. After taking the job, she joined a women’s CEO group, where female business leaders share ideas and frustrations.

‘‘We have a lot of the same concerns,’’ Basu said. ‘‘But you’ve got to be a successful CEO first and lead your company before you’re a successful woman CEO.’’

Fellow business leader Anu Shukla, who sold a start-up software company for $360 million in 2000, says she felt typecast as a marketing person at large tech companies.

‘‘When you get to the really, really top jobs, they’re all based on networks and those networks are pretty much still all men,’’ said Shukla, who is now CEO of RubiconSoft, a San Mateo, Calif., software start-up.

Women like Shukla often take time to develop entrepreneurial dreams. Eventually, pay inequities, lack of upward mobility and inflexible work schedules lead many to jump ship. During the tech boom, many joined start-ups.

‘‘The Internet boom lowered the barriers to entry for women because the tech requirements were not as hardware-driven as they were in the old days,’’ said Denise Brosseau, a founder of the Forum for Women Entrepreneurs, a Silicon Valley nonprofit organization.

Between the mid-1990s and 2002, women at the nation’s Fortune 500 companies made small but steady gains in corporate leadership, according to Catalyst, a nonprofit organization that tracks the progress of female executives. That’s less true among the top high-tech companies, where women made up 11.1 percent of corporate officers, compared with 15.7 percent at all Fortune 500 firms, according to the group’s most recent study.

‘‘Silicon Valley is supposed to be the ultimate progressive meritocracy,’’ said Kara Helander, Catalyst’s western region vice president in San Jose, Calif. ‘‘So these numbers call into question how well these companies are making use of the extraordinary talent they have with women in-house.’’

Among the 10 companies analyzed by the Mercury News, Solectron - the second-largest contract manufacturer for the computer industry - had the greatest proportion of women, in part because many hold assembly jobs. In 2000, women made up 42 percent of its work force, far greater than the average of 32 percent.

But even at Solectron, barely more than one in five managers were women, a proportion that remained steady between 1996 and 2000.

‘‘It’s something that we’re aware of, and we will make improvements over time,’’ said Solectron spokeswoman Birgit Johnston, adding that the company has training programs to help workers move up in the ranks.

At Cisco, the percentage of women dropped from 27 percent to a quarter of its entire work force, despite the company more than tripling its number of employees between 1996 and 2000.

Kate DCamp, Cisco’s senior vice president of human resources, said attracting women who are interested in technical careers is a struggle. The 19-year-old company is not yet able to ‘‘grow’’ its own talent, she said. That leaves recruiters to hire people who are already qualified to fill technical jobs - and those are still overwhelmingly men.

‘‘Women are the most underrepresented in the electrical engineering field and that for us is very relevant because we are wiring things, we are making equipment, and we are also programming and building things,’’ said DCamp, adding that Cisco will soon begin a program aimed at getting more eighth-grade girls interested in science and math. ‘‘I do not believe that the lack of women has to do with capability by any measure.’’

One of Cisco’s biggest draws for female workers is the day care center, which opened more than two years ago and has the capacity to hold more than 400 children. Next to Cisco’s campus and operated by Bright Horizons, the center is one of the few company-sponsored child-care facilities in Silicon Valley.

Parents can spend lunch hours with their children or peek in from their desktops through Cisco’s Internet Protocol TV, which allows for live video feeds from the center.

‘‘It’s just that sense of being reassured and having a window into your child’s world,’’ said manager Phyllis Stewart Pires, whose 4-year-old daughter, Ally, spends her days at the center. ‘‘Recently, my daughter had been ill, and I thought she was ready to go back. I was able to check in on her through IPTV and see that she was doing fine, so I could concentrate on my work.’’

In addition to innovative programs, women within the industry say that seeing other women in top-echelon jobs is one of the most important signs that they, too, can move up within a company.

Diana Bell, who has moved up in the ranks of HP over the past 15 years, said having female role models has been critical. ‘‘It’s important to know people of the same gender or race who have been successful because it removes a barrier,’’ said Bell, vice president for total customer experience and quality at HP. ‘‘You can use those points of commonality to get coaching and development from those people.’’

Eva Sage-Gavin, a senior vice president at Sun Microsystems, said companies need to do more than promote women. They must see their employees as ‘‘whole’’ people, she said, with lives outside of work that are important.

‘‘Flexible workplaces and schedules, really looking at employees with this idea that we believe and we trust in their commitment to Sun and their work,’’ Sage-Gavin said. ‘‘That’s what’s kept women at Sun, that’s what’s promoted women at Sun, and I think that’s what attracted women to Sun.’’

Encouraging more Latino and black students to pursue careers in high tech rests, in part, on showing them that the tech industry is a place where they could climb the corporate ladder, industry veterans say.

Without the visibility of high-ranking Latino and black managers, students may be reluctant to pursue careers at those companies.

A Mercury News analysis shows that during the tech boom, Asians, Latinos and blacks were less likely than whites to hold management positions at Silicon Valley’s 10 largest tech companies. White employees, who made up 67 percent of the overall work force at the companies in 2000, accounted for nearly four out of five of all officials and managers.

At the top levels of management there is even more of an imbalance, according to industry veterans.

‘‘If you look for Hispanics on the executive levels of HP, Agilent, you’d be hard-pressed to find one,’’ said Robert Medrano, chief executive officer of Mountain View, Calif.-based start-up PoliVec and a former general manager at HP. ‘‘I never had a minority mentor, and I had very few that mentored me to advance me. For the most part, I would have to leave a company to advance.’’

Hewlett-Packard wants to do a better job recruiting seasoned managers from outside the company, said Emily Duncan, the company’s vice president of global inclusion and diversity.

‘‘We’ve had some challenges with our process in recruiting senior-level managers,’’ Duncan said. ‘‘For a long time our procedure was to hire at the entry level, to bring people in and grow them. It takes a bit too long.’’

At Advanced Micro Devices, blacks and Latinos together represented nearly one in five workers - but just one in 17 officials or managers. Among those managers is AMD’s chief executive officer Hector Ruiz.

An AMD spokeswoman said the gap between management and other workers could be due to many blacks and Latinos having less seniority.

SAN JOSE, Calif. - If any university has tried to feed diverse workers into the tech industry, it might be San Jose State, in the heart of Silicon Valley. But to understand the challenge faced by the industry, one need only look inside San Jose State’s engineering school.

On a recent afternoon in a network analysis class of 50 students, all but nine were Asian. Angela Uzoma’s physics class is no more diverse. For a time, the third-year mechanical engineering student wondered why so many people from the class recognized her around campus. Then a friend offered an explanation:

‘‘We’re the only black girls in the class,’’ Uzoma’s friend said.

Classrooms like these help explain why Latinos and blacks made almost no progress in the tech industry during the boom, barely increasing their share of the work force. Relatively few Latinos and blacks are preparing for tech careers in the nation’s universities.

San Jose State, which recruits in heavily Latino school districts and draws two-thirds of its engineering students from community colleges, has enlisted the recruiting help of engineering students and worked with local high-tech companies to help change the complexion of its student body. But the results are mixed.

In fall 2001, enrollment data shows that 170 black students were studying engineering at San Jose State, compared with 487 Latinos, 740 whites - and 3,003 Asians. Latinos by far are the most underrepresented. Although they make up about a quarter of Santa Clara County’s residents, Latinos account for 10 percent of San Jose State’s engineering students.

In the tech industry, Latinos and blacks are just as hard to find. A Mercury News analysis of federal employment data shows that the proportion of Latinos and blacks grew from a combined 11 percent to 12 percent at the valley’s 10 highest-grossing tech companies during the boom years from 1996 to 2000. In contrast, Latinos and blacks made up nearly a quarter of the overall U.S. work force in 2000.

‘‘Somewhere over 80 percent of the jobs we hire for require some technical background,’’ said Tracy Koon, director of corporate affairs at Intel, the world’s largest maker of computer chips. ‘‘We have, kind of, two raw materials: silicon and brains. And silicon is a lot more plentiful than trained brains.’’

Tech leaders say colleges don’t have enough students like Esneider Cuellar, a mechanical engineering student at San Jose State. Born in Mexico and raised in the Bay Area, Cuellar became interested in engineering while doing construction projects with his father.

He only began to consider a high-tech career after a summer internship at IBM as a freshman. Until then, Cuellar had expected to apply the engineering skills he would learn in college to work on cars and motorcycles - the technology he saw most often growing up.

Those internships and other efforts to recruit minorities offer the best hope for building a larger pool of Latino and black workers. But Cuellar said he does not see many companies recruiting engineering students.

‘‘If there were more options for high-tech internships for Latinos, they would be filled pretty fast,’’ Cuellar said. ‘‘HP, IBM, Intel - those are the ones that I see more. They go into the engineering program, and they try to actively get diversity.’’

San Jose State’s engineering school has struggled to attract Latino and black students. Much of the recruiting relies on engineering students who volunteer their time hosting workshops and science fairs at schools in neighborhoods that are heavily Latino and black. The concept, which several Silicon Valley tech companies have embraced, is to focus attention at the secondary-school level in order to produce students better prepared for engineering studies.

The challenges don’t stop once students get into college. Horacio Alfaro, director of San Jose State’s Mathematics, Engineering, Science Achievement program, said many Latino students commute to San Jose from as far as Oakland, Calif. When students spend less time on campus, they tend to be disconnected from study groups and professors, Alfaro said.

Jared Collins, an electrical engineering student who commutes from Richmond, Calif., credits supportive high school teachers with encouraging him to pursue an engineering career.

‘‘When you have that type of atmosphere, no matter what the ethnicity of the child is, they’ll do well in it,’’ said Collins, 23. According to a recent report by the Pew Hispanic Center, Latinos and blacks in California from 1997 to 2000 were the least likely to be enrolled in college full time. They were also most likely to enroll in two-year colleges.

Ping Hsu, acting associate dean of San Jose State’s engineering school, said many students drop off the engineering track early in their college careers. That is particularly true among Latino and black students, he said.

‘‘Generally, the attrition starts the first two years. That is really the period when they have not even started the real engineering program, and there are a lot of math, physics and chemistry courses,’’ Hsu said. ‘‘Those courses tend to be very mathematically intensive or demanding, and some students are discouraged because they are not quite prepared.’’

Hewlett-Packard works closely with the MESA program at San Jose State. That relationship, as well as the company’s HP Scholars internship program, has been instrumental to efforts to broaden its pool of engineers, said Emily Duncan, vice president of global inclusion and diversity at HP.

As part of the HP Scholars program, black and Latino students receive scholarships, internships and computing equipment to help them stay productive. Duncan said the 5-year-old program has been a success: 80 percent of HP scholars who start as freshmen graduate with engineering degrees.

‘‘HP basically lays your path down by paying your tuition, giving you the tools you need to do well in school and the experience you need to get a good job when you come out,’’ said freshman HP Scholar Tony Watson, an engineering student at San Jose State.

But John Templeton, president of San Francisco-based Electron Access, said tech companies often shift too much responsibility to the educational system. After all, didn’t some of the fathers of personal computing, like Microsoft founder Bill Gates and Apple co-founder Steve Jobs, do just fine without math and science degrees?

‘‘The qualifications are generally just an excuse to avoid giving people an opportunity,’’ said Templeton, who has tracked the industry’s diversity record. ‘‘Everybody I know in technology picked it up from experience.’’

Even the industry’s best efforts at recruitment in Silicon Valley will not address a broader demographic issue: Blacks make up 2 percent of Santa Clara County’s residents. Companies that operate across the country and want to increase their proportion of black workers must look to other regions.

It can be difficult to persuade black employees to move to Silicon Valley. The region’s high cost of living and small black population turn off many prospective workers who would rather take a lower-paying job with a lesser-known company close to home.

But those obstacles can be overcome. Rosalind Hudnell, Intel’s director of diversity, said when some black engineering interns at Intel’s Sacramento, Calif.-area facility grew bored, she suggested they help coach a local youth basketball team. The move had a double benefit - the interns loved coaching, and a group of young black students learned that engineers are more than bookworms.

A few companies, including HP and Intel, have turned to historically black colleges and universities in the South to recruit talent.

Jacqueline Woods, a top-level Oracle executive, said Silicon Valley companies need to change their image of the ideal recruit. Too often, she said, tech companies assume that all the talent comes from Ivy League schools. In addition, some companies do not recruit at heavily Latino and black colleges because they say those students are not as well prepared.

‘‘If you always go and recruit at schools that have a very small ethnic population, then your pool to draw from is small,’’ Woods said. ‘‘If you really want to increase, participate at some of the premier historically black colleges and universities - the Morehouses, Howards, Spelmans. Many of those kids could get into Harvard but they go there instead because their father’s father went there.’’

HP’s approach has been to provide training and equipment to historically black colleges and other schools it supports, Duncan said, not to simply show up at recruiting fairs.

‘‘We have to invest in building those relationships,’’ Duncan said. ‘‘It is a long-term commitment. You don’t just show up and cross your fingers. That’s really not how success happens.’’