European M.B.A. programs have been thriving in recent years, but they are struggling with a problem that long has plagued American business schools too: Women are staying away in droves.

Theories abound to explain why more women aren't seeking a credential that could boost their careers and earning power. Some business-school experts believe European schools struggle even more than M.B.A. programs in the U.S. to bring the numbers up because many businesses on the Continent are perceived as less friendly to women executives than American firms.

Others say it reflects the timing of the European degree, which students generally seek in their early 30s, a bit older than the U.S. average and a time when many women are thinking about having children.

Both in Europe and the U.S., some experts cite a perception that M.B.A. programs are overly macho and too focused on competition, and note that women are less likely than men to enter sectors where an M.B.A. is highly valued, such as investment banking and consulting. Some school administrators point out that while many women relocate when their husbands go to business school -- often moving with children -- fewer men are willing to do so.

Whatever the underlying causes, the result is apparent: Female M.B.A. enrollment in European business schools is stuck stubbornly between 25% and 30%, said Jeanette Purcell, chief executive of the Association of M.B.A.s, an international body based in London whose members include about 130 business schools world-wide. The University of Cambridge's Judge Business School says the figure is even lower for Europe's elite B-schools, at 23%. In the U.S., women's representation in M.B.A. programs long has hovered around 30%.

"Business schools are extremely concerned about the level of participation by women," Ms. Purcell said. While many M.B.A. programs are changing to try to draw more women, she predicted progress would remain slow.

At Spain's Instituto de Empresa, which with a 36% female M.B.A. class is one of the more gender-balanced schools, officials offer scholarships to women, run electives on issues women are likely to face in the business world and make a point of teaching with case studies in which females are main players. Helping women students to tap into alumni networks and connect with mentors in high-ranking business jobs also is a priority.

Celia de Anca, director of the school's Center for Diversity in Global Management, said worries about balancing work and family are the biggest factors keeping female applicants away. Many of today's students, she said, feel their elders were forced to choose between children and demanding work and want to avoid such dilemmas themselves by finding jobs that are easier to balance with responsibilities at home.

Officials at several schools noted that the proportion of women varied widely among applicants of different nationalities, with the highest numbers often coming from the U.S. That may reflect that American women have entered and risen through the business world in greater numbers than their European or Asian counterparts, they said. "In Europe, there's much more cultural bias that women have to fight through to say, 'Yes, I want to have a career,' " said Janet Shaner, a spokeswoman for IMD Business School in Lausanne, Switzerland.

Labrina Barmpetaki, a student at Britain's Lancaster University Management School, said many women who consider M.B.A.s lack the self-confidence needed to leave a secure job and leap into a degree program. Often their families may not back such decisions, especially in her native Greece, she said.

Lancaster is one of many schools that have worked hard to shake that image, shifting from a traditional focus on technical and quantitative teaching to emphasize "soft skills" that course directors believe play to many women's strengths. Those abilities, like leadership, communication and team management, are increasingly prized by employers, they add.

The eight-year-old program at Cambridge's Judge school worked from the start to appeal to women, trying hard to avoid an atmosphere of ruthless one-upmanship. This year, its M.B.A. class is 34% female. "We thought what we want to do is bring collaboration and a sense of community and joint purpose into the program," said Simon Learmount, admissions director.

One disincentive for women may be the gap that still exists between the salaries of male and female M.B.A.s, said Ms. Purcell. And some companies may be less likely to pay for female employees to go back to school, possibly because they fear the women eventually will stop work to have children, she said. While business schools are doing everything they can to draw more women, she doesn't see a significant jump in numbers until conditions improve for women in the wider business world.