Whereas most gay men in Australia know their HIV test result, a consistent minority do not. From Gay Community Periodic Surveys (n=6831) conducted during 1998 in the 5 largest cities, those who did not have HIV test results (13.3% overall) comprised 10.0% in Sydney, 15.7% in Melbourne, 13.6% in Brisbane, 15.2% in Perth and 14.0% in Adelaide, representing a significant difference between cities (P < 0.001). Gay men who did not have HIV test results differed from those who did in several ways. They were on average younger (31 vs 35 years, P<0.001) and less likely to be in professional occupations (P<0.001). They were less likely to identify themselves as 'gay' (P<0.001), spent less time with other gay men (P<0.001) and had fewer gay friends (P<0.001). They had sex with fewer different men 'in the previous 6 months' (P<0.001) and were more likely to be in a monogamous relationship or without sexual partners at the time of the survey (P<0.001). With respect to both regular and casual partners, they were more likely (P<0.001) to have 'no such partner'/'no anal intercourse' rather than 'anal intercourse' (either always protected or sometimes unprotected). These differences between gay men who did and did not have HIV test results were confirmed in a logistic regression (apart from 'amount of free time spent with gay men' and 'relationship status' which were accounted for by closely correlated variables in the reduced logistic model). Social and sexual environment appears to exert an influence on HIV testing rather than sexual risk per se.