The objective of this study was to assess the impact of successes in the medical treatment of HIV disease on the perceptions of high-risk gay and bisexual men attending an anonymous testing site towards becoming infected with HIV and on their decisions to have unsafe sex. A cross-sectional survey with a face-to-face interview and self-recorded information was used. A convenience sample of high-risk men seeking anonymous HIV antibody counselling was recruited for an intervention study. To be eligible, men had to have a history of at least one previous negative antibody test and unprotected anal intercourse within the last year. Upon enrollment, subjects were asked about the impact of new treatment developments on their decisions to engage in high-risk sex both in the recent past and in the future. In general, neither the recent successes in treating HIV nor the availability of combination therapy had any impact on the men's decisions about safe sex, although a minority of men reported less concern about becoming HIV-positive. Also, some men reported already having taken more risk. In conclusion, a small number of men in this high-risk population have increased risk behaviour as a result of recent treatment advances. These results merit continued monitoring.