Objective: To examine the interplay between situational, social and ps
ychological factors in gay men's decisions about HIV risk behaviour, u
sing multiple hypothetical situations. Method: The sample included 79
gay men from Sydney recruited through flyers, press advertisements or
personal contact at gay venues. Subjects were presented with 20 hypoth
etical situations graphically on a computer, which included different
levels of attraction to partner, intoxication, attractiveness to partn
er, condom availability, desire for anal sex by subject, insistence of
partner on using a condom and time constraints in each situation. Sub
jects used a computerized graphic rating scale to indicate the likelih
ood of unprotected anal sex in each situation, the frequency with whic
h they had experienced the hypothetical situation in real life and sat
isfaction with their response. The probability of having unsafe anal s
ex in any given situation was the dependent variable. All other variab
les were predictors. Results: A vector of predictors accounted for 30%
of the variance (r = 0.54). Ratings of the probability of anal sex in
creased with the frequency that subjects had experienced hypothetical
situations in real life, attraction to partner, attractiveness to part
ner and time elapsed since real life experience similar to the hypothe
tical one. Ratings of the probability of anal sex decreased with condo
m availability. Conclusions: Our results suggest that interventions mu
st address the way that individuals interact with their partner and th
eir environment in order to be successful.