HIV-negative gay men at risk.
D000293:Adolescent; D000328:Adult; D015658:HIV Infections / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D018023:HIV Seronegativity; D006266:Health Education; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D012307:Risk Factors; D012309:Risk-Taking