Although occupational sex segregation has decreased over the last 25 years, it is still a major social concern primarily because of the role it plays in perpetuating the gender wage gap. This paper uses data from the Wisconsin Longitudinal Study, a study that followed a random sample of 10,317 high school graduates, to assess the determinants of women's movement into and out of male-dominated occupations. In this study, the gender type of occupations changes with time; that is, the shifting gender compositions of occupation categories from 1960 to 1990 is taken into account. Event history analysis is used to ascertain the relative risk of a woman's entering and leaving a male-dominated occupation. The hazard rates are then used to project the change expected in the overall distribution of women in male-dominated and nonmale-dominated occupations, and periods out of the labor force, over time. The analysis evaluated gender role socialization and neoclassical economic theories of occupational sex segregation by including a number of covariates that measure background characteristics and the timing of life course events of the woman, characteristics of jobs the woman enters over her career, and indicators of opportunity in the local labor market. The results show support for sex role socialization as an explanation for women's movement into sex-atypical occupations, and show that having aspirations for a male occupation, in particular, is associated with increases in the percentage of women employed in male-dominated occupations over time. Neither neoclassical economic theories nor demand-side theories are well-supported. These results are compared with those of J. A. Jacobs (1989), and it is concluded that sex role socialization is important in perpetuating occupational sex segregation. (Contains 7 tables, 6 figures, and 45 references.) (Author/SLD)