Different cohorts of gay/bisexual men experience unique developmental factors given their distinct socio-historical contexts. This study examined the moderating effects of age on three psychosocial predictors of HIV risk behavior and substance use. Analyses drew on data from a study of substance using HIV-negative and unknown status gay/bisexual men (N= 302) at risk for HIV infection. Anxiety was a strong independent predictor of sexual risk and substance use, and its effects on the sex risk outcomes were moderated by age, such that older and more anxious participants had more frequent instances of sexual risk. Identification with the gay community protected against HIV risk, and its effects on sex risk outcomes were moderated by age, such that younger participants who identified with the gay community reported less sexual risk. Understanding HIV risk within socio-historical contexts is essential in tailoring prevention by taking into account recipients' ages.