Men who have sex with men (MSM) are substantially impacted by HIV/AIDS in the United States. Alcohol use is frequently studied as a predictor of sexual risk in MSM, but findings for this association have been mixed. Developmental differences in this effect may help to explain equivocal findings. 143 MSM (analytic sample 137) ages 16-40 completed weekly diaries of sexual encounters and associated situational factors for 12 weeks. Analyses were conducted with Hierarchical Linear Modeling. Alcohol use before sex was not associated with sexual risk across all participants. Participant age moderated this effect; alcohol use before sex was associated with increased odds of sexual risk in younger MSM only. These analyses expand on previous findings by utilizing a wider age range than most prior studies and adjusting for the effects of several theoretically-selected covariates. Young MSM are an important group to target for addressing alcohol use in the context of sexual behavior.