Background: The present study sought to determine the level of undiagnosed HIV infection within a community setting of men who have sex with men (MSM) and identify any associated sexual risk behaviours. Methods: A total of 427 MSM were recruited in sex-on-premises venues (SOPV) and gay bars within the inner city of Brisbane. An additional 37 MSM were recruited in a smaller, regional centre (Toowoomba). Oral fluid testing for HIV antibodies was undertaken using the Orasure collection system and assay. Each participant was invited to complete a brief behaviour questionnaire and submit an oral fluid specimen. Confirmed serology results were linked to reported sexual behaviours, testing patterns and HIV status. Results: Of the 464 men surveyed, 33 identified as HIV-positive, and all of these were reactive by the Orasure assay. A further eight people who identified as negative or unknown serostatus, had confirmed Orasure reactive results, resulting in 1.9% of the ‘non-HIV positive’ MSM sample unaware of their positive HIV status. Therefore, 19.5% of the total confirmed HIV-positive individuals were not aware of their true serostatus. Conclusions: A significant minority of HIV-positive MSM are currently unaware of their positive serostatus. However, an analysis of their risk behaviour does not seem to indicate any significant difference to those who are HIV-negative. Interestingly, 86% of those who were unaware they were HIV-positive identified that they had been tested in the previous 6 months and all of them claimed to have been tested in the previous 2 years.