The article explores sex segregation by field of study in 44 countries, challenging the notion that socioeconomic modernization leads to a "degendering" of public-sphere institutions. Instead, it argues that sex typing of curricular fields is stronger in more economically developed contexts. Two cultural forces—gender-essentialist ideology and self-expressive value systems—combine to create a new form of sex segregation regime in advanced industrial societies. Multivariate analyses suggest that structural features of postindustrial labor markets and modern educational systems support the cultivation, realization, and display of gender-specific curricular affinities. While women have gained majority status in new college and university graduates in many industrial countries, sex segregation persists, with women underrepresented in science, engineering, and technical programs. Recent comparative analyses suggest that some forms of segregation are more pronounced in the most socially or culturally modern societies. The authors argue that conventional evolutionary models of women's status cannot fully explain cross-national and historical variability in sex segregation by field of study because they underestimate the enduring cultural force of gender-essentialist ideology. The segregative effect of gender-essentialist beliefs is intensified by a strong Western cultural emphasis on individual self-expression and self-realization. Because gender remains central to human identity, self-expressive value systems tend to encourage the development and enactment of culturally masculine or feminine affinities. Structural features of modern educational systems and labor markets may also promote gender-differentiated aspirations and their realization. The study uses international data and log-linear methodology to model cross-national variability in sex segregation by field of study as a function of cultural gender beliefs and macrolevel features of educational systems, economies, and labor markets. The results show a general tendency for greater segregation of academic fields in more economically developed contexts. However, multivariate analyses reveal important discontinuities between developing/transitional and advanced industrial societies in the processes generating this form of gender inequality, suggesting that distinct sex segregation regimes may operate in "materialist" and "postmaterialist" societies. The article discusses the cultural and structural forces shaping cross-national variability in sex segregation by field of study, including cultural value systems that celebrate gender difference, expansion and structural diversification of higher education systems, and postindustrialism and the growth of "female-demanding" occupational sectors. It also explores the effects of gendered curricular affinities, economic development, and tertiary diversification on sex segregation. The study finds that sex segregation is more pronounced in advanced industrial societies, where self-expressive values and gender-essentialist beliefs combine to reinforce gendered curricular choices. The results challenge the notion that socioeconomic modernization leads to a general weakening of gender differentiation.The article explores sex segregation by field of study in 44 countries, challenging the notion that socioeconomic modernization leads to a "degendering" of public-sphere institutions. Instead, it argues that sex typing of curricular fields is stronger in more economically developed contexts. Two cultural forces—gender-essentialist ideology and self-expressive value systems—combine to create a new form of sex segregation regime in advanced industrial societies. Multivariate analyses suggest that structural features of postindustrial labor markets and modern educational systems support the cultivation, realization, and display of gender-specific curricular affinities. While women have gained majority status in new college and university graduates in many industrial countries, sex segregation persists, with women underrepresented in science, engineering, and technical programs. Recent comparative analyses suggest that some forms of segregation are more pronounced in the most socially or culturally modern societies. The authors argue that conventional evolutionary models of women's status cannot fully explain cross-national and historical variability in sex segregation by field of study because they underestimate the enduring cultural force of gender-essentialist ideology. The segregative effect of gender-essentialist beliefs is intensified by a strong Western cultural emphasis on individual self-expression and self-realization. Because gender remains central to human identity, self-expressive value systems tend to encourage the development and enactment of culturally masculine or feminine affinities. Structural features of modern educational systems and labor markets may also promote gender-differentiated aspirations and their realization. The study uses international data and log-linear methodology to model cross-national variability in sex segregation by field of study as a function of cultural gender beliefs and macrolevel features of educational systems, economies, and labor markets. The results show a general tendency for greater segregation of academic fields in more economically developed contexts. However, multivariate analyses reveal important discontinuities between developing/transitional and advanced industrial societies in the processes generating this form of gender inequality, suggesting that distinct sex segregation regimes may operate in "materialist" and "postmaterialist" societies. The article discusses the cultural and structural forces shaping cross-national variability in sex segregation by field of study, including cultural value systems that celebrate gender difference, expansion and structural diversification of higher education systems, and postindustrialism and the growth of "female-demanding" occupational sectors. It also explores the effects of gendered curricular affinities, economic development, and tertiary diversification on sex segregation. The study finds that sex segregation is more pronounced in advanced industrial societies, where self-expressive values and gender-essentialist beliefs combine to reinforce gendered curricular choices. The results challenge the notion that socioeconomic modernization leads to a general weakening of gender differentiation.