Background: Standard two-step HIV testing is limited by poor return-for-results rates and misses high-risk individuals who do not access conventional testing facilities. Methods: We describe a community-based rapid HIV testing programme in which homeless and marginally housed adults recruited from shelters, free meal programmes and single room occupancy hotels in San Francisco received OraQuick Rapid HIV-1 Antibody testing (OraSure Technologies, Bethlehem, PA, USA). Results: Over 8 months, 1614 adults were invited to participate and 1213 (75.2%) underwent testing. HIV seroprevalence was 15.4% (187 of 1213 individuals) overall and 3.5% (37 of 1063) amongst high-risk individuals reporting no previous testing, a prior negative test, or previous testing without result disclosure. All 1213 participants received their results. Of 30 newly diagnosed persons who received confirmatory results, 26 (86.7%) reported at least one contact with a primary healthcare provider in the 6 months following diagnosis. Conclusions: We conclude that community-based rapid testing is feasible, acceptable and effective based on the numbers of high-risk persons tested over a short period, the participation rate, the prevalence of new infection, the rate of result disclosure, and the proportion linked to care. (Authors)