Family scholars have focused on the onset of sexual activity early in the life course, but little is known about the cessation of sexual activity in relationships in later life. We use event-history analysis techniques and logistic regression to identify the correlates of sexual inactivity among older married men and women. We analyze data for 1,502 married people from the National Social Life, Health, and Aging Project, a nationally representative sample of 3,005 noninstitutionalized American men and women ages 57 to 85. We find 29% of the married persons report no sexual activity for the previous 12 months or more. Relationship duration, chronological age, and poor physical health are all independently associated with sexual inactivity. Characteristics such as marital happiness, premarital cohabitation, and remarriage are also associated with levels of inactivity or activity. Analyses also point to gender differences in the correlates of sexual inactivity. (Contains 4 tables and 1 note.)