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...