- This paper examines the macro-level relationship between female labor force activity and the sex differential in mortality among developed nations. Discrimination, protection, and null relationship hypotheses are tested using aggregate data for 18 high income nations over 7 time points from 1950 to 1980. High levels of female labor force activity--controlling for a variety of general social conditions--increase the longevity advantage women have over men. In some models the effects are immediate; in other models the effects occur after a substantial lag; but in no cases are there harmful effects for women's longevity. Also important for the differential are consumption of cigarettes and alcohol, and the level of income inequality in a society.