This prospective study examined the effect of widowhood on physical activity by comparing widowed elders to health status-, age-, and sex-matched married controls. Participants included 396 married controls and 396 widows/widowers age 64-91 (M age = 72.7 years) who experienced the death of their spouse while participating in the Cardiovascular Health Study. Compared to married controls, widowed men, but not women, were more likely to increase their physical activity following the death of their spouse. However, this increased level of activity was not sustained and declines as time since spousal death passes. Moreover, during the year before spousal death, soon-to-be widowed men, but not women, increase their physical activity. Our results suggest that widowed men experience significant changes in physical activity and that the transition to widowhood contribute to these changes.