Khris Brown started her own voice production business eight years ago with just $100 and now takes in about $100,000 in annual revenue. Her work -- casting and directing voices for films and video games -- has been featured in high-profile movies like "Minority Report" and "Star Wars." She could add more clients if she wanted.

But Brown is happy keeping the business small, with just a couple of occasional contract employees. "I'd rather have time to breathe and do my best work than a high income that demands I'm spread too thinly," said Brown, 35, whose firm is KBA Voice Production in San Francisco.

Is Brown a small-business success story?

Or is she an example of what's wrong with America's female business owners?

Women's business advocates recently joined with companies such as American Express in a national campaign to encourage more women to expand their businesses to the million-dollar sales mark.

They point to the fact that women today are starting businesses at a higher rate than men. But women remain underrepresented when it comes to ownership of midsize and large companies.

For instance, U.S. Census data show that fewer than 4 percent of women-owned businesses have revenue of $500,000 or more per year, compared with 11 percent of businesses owned by men.

And 46 percent of women-owned businesses are tiny enterprises with revenue of less than $10,000 per year, compared with 30 percent of men-owned businesses.

Leaders of the Make Mine a Business campaign say that both society and individuals will benefit if more women manage to build large businesses.

The cornerstone of their campaign is a national contest to select 40 women-owned businesses with plans to grow to $1 million. Winners will receive up to $45,000 in financing, plus mentoring and marketing help.

Sponsors include Count Me In, a nonprofit group that makes microloans to female entrepreneurs, American Express, Cisco Systems, QVC and the National Association of Women Business Owners.

"If we get a million women-owned businesses at the million-dollar level, that will mean 4 million new jobs and $700 billion added to the economy," said Nell Merlino, CEO of Count Me In, who previously created Take Our Daughters to Work Day.

Some observers question whether there is a need to single out women business owners for help.

"The world is an oyster for women right now," said Sally Pipes, president of the Pacific Research Institute, a free-market think tank. "The opportunities are there, whether they want them or not. ... We should focus on removing barriers that keep both men and women from starting their own businesses, such as regulations and the tax burden."

But others say the million-dollar campaign is shining a welcome spotlight on a neglected slice of the business world -- enterprises that have moved beyond "start your own business" workshops but still lack capital and other tools for growth.

"In the 1990s, there was a government focus on welfare-to-work, with a lot of attention to micro-financing," said Darlene Crane of PCI Crane Consulting in Hayward, who is studying the needs of businesses in the $50,000-to-$10 million range. "Then, once you get above $10 million, you're considered investment quality. There is a 'forgotten middle' of companies with five to 10 employees and a passion to grow but not a lot of money to pay for resources."

While there is no question that relatively few women own large businesses, there is considerable debate and speculation over the reasons.

Some reasons suggested by experts are external, such as discrimination. But more of the commonly cited reasons are internal, such as women's skills, goals, fears and priorities. "A lot of this is a mind-set," Merlino said.

Among the speculations:

-- Women's recent entry into business ownership. As late as 1974, women were not allowed to hold credit in their own names in many states.

"Men have been in business longer, and part of what helps you get to a larger size is just time," said Sharon Hadary, executive director of the Center for Women's Business Research in Washington.

-- Lingering discrimination. Banks and other business organizations have opened their doors to women, and many actively court female business owners as a market. But some women still claim to have trouble penetrating "old boy networks" of potential customers and clients.

-- Lack of financial skills. "To grow your business, you really need to understand the numbers," Merlino said. "Often women get very enamored with the product or service they're providing, and they aren't as enamored with the numbers."

-- Fear of taking on debt. A study by the Center for Women's Business Research showed that women were less likely to use or seek credit than men, even when running comparably sized businesses. "A lot of women are so proud of themselves and say, 'I've never borrowed any money,' " Merlino said. "But to grow, you've got to reach out to other people" for capital.

-- Different goals. While both men and women go into business for reasons like independence and flexibility, women typically bear more household and parenting responsibilities than men do. Many women choose a small or part-time business as a way to accommodate their family commitments.

Barbara Moser is one. Moser left a big San Francisco law firm and started a two-lawyer practice in 1995 to have a flexible schedule for raising her children. "My partner and I shared a vision of having a happier work life where we could make our own choices," she said.

Her firm, Kaye Moser, has grown to three attorneys and $900,000 in revenue. But Moser doesn't want to see it get much bigger. "We turn away a lot of business, but we have a good life and are making what we want. ... I eat, sleep and breathe my business on the one hand. But I also try to take off one or two days a week to do my family business."

For every female entrepreneur like Moser or Brown who chooses to stay small, however, there are others who are eager for growth.

The Make Mine a Business campaign has so far received more than 500 applications, including 102 from the Bay Area. The group will select 20 winners in San Francisco Friday at a conference of the National Association of Women Business Owners, and another 20 later this year at a New York event.

Sheila Moon is one of those applicants. Moon started a fashion business in 2003, designing bike and athletic apparel that is now sold in 110 retail stores. With sales of $144,000 last year, her goal is $280,000 this year and $1 million in 2008.

"The biggest thing that's held me back is lack of access to capital," said Moon, 41, whose company is Sheila Moon Athletic Apparel in San Francisco. "I financed a lot of the startup through credit cards and am still having to pay that down."

Moon also acknowledges being limited by her own attitudes, such as a reluctance to delegate work to other people so she can focus on strategy and growth.

"So far, I've had a small-business mentality," she said. "I need to get out of that and think big -- think of myself as a big business."

The "small-business mentality" cited by Moon is exactly what Merlino and her allies hope to change.

"Millions of women are happy just being their own boss, but maybe there's someone in the booth next to them with visions of being sold globally, and you can't do that on $100,000 revenues," Merlino said.

"I want to make sure that the woman who starts a 15-hour-per-week business to be home with little kids knows what she can do if the business catches on," Merlino said. "I want to help her find the path. I don't want her to think that the 15-hour week is her only option."