Objective-Research has suggested a weak association between depression and sexual risk behavior in men who have sex with men (MSM). The purpose of this study is to investigate the relationship between within-person fluctuations in depression and well-being and episodes of sexual risk-taking among HIV-positive MSM.Methods-One hundred and six sexually active HIV-positive MSM living in New York City completed a structured weekly survey over six weeks. In weeks 1, 3, and 5, they responded to items assessing their sexual behavior, depression and well-being in the prior week. Multi-level logistic regression analyses were conducted to explore the relationship between changes in levels of depression and well-being and episodes of unprotected anal intercourse (UAI).Results-Within-person deviations from participants' average levels of depression and wellbeing were associated with the probability of risk. The probability of a risk episode was higher in weeks when depression was higher than participants' average levels (any UAI episode: OR = 1.71, 95% CI [1.00-2.90], p < .05; serodiscordant UAI episode: OR = 2.49, 95% CI [1.31-4.73], p < . 05). The probability of a risk episode was lower in weeks when well-being was higher than participants' average levels (any UAI: OR = 0.40, 95% CI [0.22-0.74], p < .05; serodiscordant UAI: OR = 0.42, 95% CI [0.22-0.81], p < .05). Between-person differences in depression and well-being were not associated with risk episodes (all ps > .05).Conclusions-This study is among the first to examine the association of within-person changes in depression and well-being with sexual risk behavior in a diverse sample. It contributes new evidence to literature exploring the relationship between depression and sexual risk. Future research should employ longitudinal designs to explore pathways linking within-person changes in depression with risk behavior. Keywords depression; well-being; HIV/AIDS; men who have sex with men; sexual risk behavior