The 1991 National Survey of Men was conducted to examine issues related to sexual behavior and condom use among U.S. men aged 20 to 39. Data collection and processing took place between March 1991 and January 1992. This survey was intended to serve as a baseline survey for a longitudinal study. Face-to-face interviews asked respondents about demographic information sexual initiation and current exposure; current wife or partner; previous marital relationships; other non-marital sexual partners; nonsexual romantic partners; health and risk-taking behavior; attitudes, perceptions, and knowledge of health-related and contraception-related issues. A set of self-administered questions assessed self-esteem, locus of control and attitudes toward marriage. This baseline study includes a total of 3,321 cases and 2,131 variables.