Over the past five decades, the organization of women's lives has changed dramatically. Throughout the industrialized world, paid work and family biographies have been altered as the once-dominant role of homemaker has given way to the role of secondary, dual, or even primary wage-earner. The attendant changes represent a mix of gains and losses for women, in which not all women have benefited (or suffered) equally. But little is known about the health consequences. This article addresses that gap. It develops a “situated biographies” model to conceptualize how life course change may influence women's health. The model stresses the role of time, both as individual aging and as the anchoring of lives in particular historical periods. “Situating” biographies in this way highlights two key features of social change in women's lives: the ambiguous implications for the health of women as a group, and the probable connections to growing social and economic disparities in health among them. This approach lays the groundwork for more integrated and productive population-based research about how historical transformations may affect women's health.