This controlled prospective study assessed the effectiveness of a sexual health approach to HIV prevention for men who have sex with men (MSM). Participants (N = 422 Midwestern MSM) were randomly assigned to the intervention group, who participated in a 2-day comprehensive human sexuality seminar designed to contextually address long-term risk factors and cofactors, or to the control group, who watched 3 hours of HIV prevention videos. Risk behavior during the preceding 3 months was measured at baseline, 3-month follow-up, and 12-month follow-up. Any unprotected anal intercourse outside a long-term seroconcordant relationship was the dependent variable. Of the total, 14%-24% of the participants were considered at risk of acquiring or transmitting HIV. At the 12-month follow-up, the control reported a 29% decrease in the use of condoms during anal intercourse; the intervention group reported an 8% increase (t = 2.546; p = .015). The sexual health seminars appear a promising new intervention at significantly reducing unprotected anal intercourse between men.