Although the number of women receiving doctorates and in academic positions has increased over the past 20 yr, females still are under-represented on university faculties. The extent of and reasons for this inequity are discussed. There are four critical periods that influence the retention of women in science: early childhood, adolescence, college, and the graduate school/job entry period. For each of the later three periods, the paper addresses the relationship between self-esteem and job performance, the quality and impacts of classroom interactions, and the role of the advisor/mentor. In addition, some of the difficulties in combining career and family responsibilities are considered. Effective networking and mentoring play an important role at the faculty level. If our goal is to have a scientific community open equally to all members of the general population, it is necessary to keep adolescent girls involved in math and science and to maintain their self-esteem. New faculty need to be more completely included in departmental and professional activities through both formal programs and good neighborliness on the behalf of existing faculty.