To the extent that men who have sex with men (MSM) use the Internet, it serves as a promising medium for behavioral intervention. The present study sought to investigate the efficacy of a web-based skills training and motivational intervention in a randomized trial (N = 112) conducted completely online. After a detailed assessment, MSM were randomly assigned to an online intervention or a control website. The experimental intervention consisted of risk assessment and feedback, motivational exercises, skills training, and education while the control intervention focused on relaxation skills. Follow-up data were collected 3 months later and analyzed with repeated-measures MANOVA. Although both groups evidenced across-the-board reductions in unprotected sex, perhaps due to the detailed assessment, the experimental group showed greater reductions with the riskiest partners, those of positive or unknown serostatus. Thus, this study gives preliminary evidence that a brief web-based intervention offering cognitive behavioral skills training and motivational enhancement can effectively reduce sexual risk in MSM.