This study examined the unique contributions of masculinity and men's perceptions of the normativeness of men's and women's health behaviors in predicting men's self-reported health behaviors. One hundred and forty men aged 18-78 were recruited from 27 unmoderated and moderated Internet listservs of potential interest to men. They completed measures on-line assessing masculinity, their perceptions of normative health behaviors for men and women, and 8 health behaviors (i.e., alcohol abuse, seatbelt use, tobacco use, physical fighting, use of social support, exercise, dietary habits, and receipt of annual medical check-ups). Findings suggest that masculinity and the perceived normativeness of other men's health behaviors significantly predicted participants' own health behaviors beyond that accounted for by socio-demographic variables (e.g., education, income). Perceptions of the normativeness of women's health behaviors were unrelated to participants' health behaviors. The findings support previous research which has found that traditional masculine gender socialization and social norms models encourage men to put their health at risk, and suggest directions for health promotion efforts when working with men.