This article seeks to explain the substantial increases in older men's labor force participation rates observed since the mid-1990s. Using data from the United States, Canada, and the United Kingdom, I exploit the cohort effects driving recent increases in older women's participation rates to identify the effect of a wife's participation decision on her husband's participation decision. I then decompose the changes in older married men's participation rates, demonstrating that husbands' responses to increases in wives' participation in the labor force can explain one-fourth, one-half, and one-third of the increase in the United States, Canada, and the United Kingdom, respectively. (c) 2008 by The University of Chicago. All rights reserved..