STUDY OBJECTIVE: Examine the relation between aspects of gender equality and population health based on the premise that sex differences in health are mainly caused by the gender system. SETTING/ PARTICIPANTS: All Swedish couples (98 240 people) who had their first child together in 1978. DESIGN: The exposure of gender equality is shown by the parents' division of income and occupational position (public sphere), and parental leave and temporary child care (domestic sphere). People were classified by these indicators during 1978-1980 into different categories; those on an equal footing with their partner and those who were traditionally or untraditionally unequal. Health is measured by the outcomes of death during 1981-2001 and sickness absence during 1986-2000. Data are obtained by linking individual information from various national sources. The statistical method used is multiple logistic regressions with odds ratios as estimates of relative risks. MAIN RESULTS: From the public sphere is shown that traditionally unequal women have decreased health risks compared with equal women, while traditionally unequal men tend to have increased health risks compared with equal men. From the domestic sphere is indicated that both women and men run higher risks of death and sickness when being traditionally unequal compared with equal. CONCLUSIONS: Understanding the relation between gender equality and health, which was found to depend on sex, life sphere, and inequality type, seems to require a combination of the hypotheses of convergence, stress and expansion.