It is important to know if optimism about HIV treatments is widespread and whether it is growing. To this end, cross-sectional surveys of gay men were conducted 6-monthly in Sydney between February 1997 and February 1999 (n = 3012). Recruitment was consistent at 4 gay community venues. The participants responded True, False or Unsure to 5 statements about the effectiveness of HIV treatments (2 items), and transmission (2 items) and 'worry' (1 item) in the context of treatments. In terms of effectiveness, HIV-positive men were more likely than non-positive men to dismiss 'cure' (P < 0.05) and more likely to support 'treatments prevent serious illness' (P < 0.001). Uncertainty about effectiveness decreased over time (P < 0.001 for each item). In terms of transmission, HIV-positive men were more likely than non-positive men to reject notions of reduced infectivity (P < 0.001). Over time, there was less uncertainty among non-positive men about undetectable viral load and transmission possibilities (P < 0.001). Overall, HIV-positive men were less 'worried' than non-positive men (P < 0.001) but there were no changes over time. On the whole, gay men in Sydney are now less uncertain about highly active antiretroviral therapies (HAART) than at the time of their introduction. Most men remain sceptical that these treatments can cure HIV infection and prevent HIV transmission, but in regard to managing illness among those infected, some initial uncertainty is being replaced by a growing optimism about the efficacy of treatments.