We examined differences over time in Sydney gay men's unprotected anal intercourse, particularly with a view to investigating any behavioural changes after the recent improvements in anti-retroviral therapies. Trends in unprotected anal intercourse were monitored through the Sydney Gay Community Periodic (cross-sectional) Surveys which were conducted at six-monthly intervals between February 1996 and February 1998. Gay men (n=2,863) were recruited and self-completed a short questionnaire at three gay venues and a sexual health clinic. There was a significant increase in unprotected anal intercourse with casual partners (but not with regular partners), applicable to both HIV positive and HIV negative men. Sexual practice was generally unrelated to ideas about recent advances in viral load testing and combination therapies.