Background The Australian HIV and sexually transmissible infection (STI) behavioural surveillance system (the repeated cross-sectional Gay Community Periodic Surveys, GCPS) has been conducted since 1998 and covers six main Australian jurisdictions. In this paper, we review its history and methodology, and the available indicators, their trends and their use. Methods:We describe the design and history of GCPS. For analyses of indicators, we use Pearson’s χ2-test and test for trend where appropriate. Results: About 90% of gay men in Australia have been tested for HIV (60% to 70% of men who were not HIV-positive) have been tested as recommended in the preceding 12 months. STI testing levels (~70% in the preceding 12 months) are high, but remain insufficient for STI prevention. In general, unprotected anal intercourse with regular (UAIR) and casual (UAIC) sex partners has increased over time. The prevalence and increasing trends in UAIR were similar across jurisdictions (P-trend <0.01), while trends in UAIC differed across the states: during 2001–08, UAIC declined in NSW (P-trend <0.01) and increased elsewhere (P-trend <0.01). Trends in UAIC were associated with HIV diagnoses. Conclusion: This review of the design, implementation and findings of the Australian HIV/STI behavioural surveillance highlights important lessons for HIV/STI behavioural surveillance among homosexual men, particularly the need for consistent data collection over time and across jurisdictions. Investment in systematic behavioural surveillance appears to result in a better understanding of the HIV epidemic, the availability of a warning system and a better targeted HIV prevention strategy.