Successful antiretroviral treatments, achievements in gay acceptance and human rights, and internet use have prompted changes in gay socialising which create potential challenges for engaging with gay men for HIV surveillance and research. We used data from the Australian behavioural surveillance and explored (i) the relationship between community engagement and HIV related practices, and (ii) time trends in gay men's engagement with the gay community. Analyses were conducted using log-binomial regression and chi-square test for trend. The proportion of men who socialized mainly with gay men declined and the Internet use to connect with sex partners increased over time. Gay social engagement was associated with HIV positive serostatus, unprotected anal intercourse with regular partners and a high frequency of HIV/STI testing. Our findings indicate a shift in how gay men socialise and find partners. We discuss the challenges for ongoing engagement with gay men for behavioural surveillance and HIV research.