I test two explanations of occupational sex segregation that have been generated from the neoclassical theory of human capital. Polachek argues that segregation results because women whose employment is intermittent maximize lifetime earnings by choosing occupations with low depreciation during time spent at home. Zellner hypothesizes that many women optimize lifetime earnings by choosing occupations with high starting wages but low wage appreciation, while men optimize in occupations with high appreciation. Both theses assert that men and women have a pecuniary reason to choose occupations traditional for their sex. Regression analyses using 1974 data from the Panel Study of Income Dynamics refute both theses. Controlling for education and experience, women have higher lifetime earnings if they work in predominantly male occupations.