HIV testing is associated with increased knowledge and reductions in sexual risk behaviours among men in Cape Town, South Africa.

HIV testing benefits those who test positive, allowing them to receive treatment, but the benefits for those who test negative remain controversial. We evaluated the impact of testing on HIV knowledge and sexual risk among men in South Africa. Men were recruited from townships outside Cape Town and completed a survey that assessed testing history, knowledge, and sexual behaviours. Among the 820 participants, 516 (63%) reported being tested (82% tested negative, 6% tested positive, and 12% unknown). Compared to those who had never been tested for HIV, men who tested for HIV were more knowledgeable about HIV transmission, but did not differ on sexual risk behaviour. Knowledge moderated the effect of testing on sexual risk such that men reported fewer sexual partners (incidence rate ratio (IRR) = 0.91, 95% CI = 0.84, 0.98) and fewer unprotected anal sex events (IRR = 0.81, 95% CI = 0.66, 1.00) if they had been tested for HIV and were knowledgeable about HIV transmission. For men testing HIV-negative, knowledge predicted fewer sexual risk behaviours. Previous HIV testing is associated with enhanced knowledge, which moderates sexual risk behaviour among South African men living in Cape Town. Results suggest that HIV testing may increase knowledge and lead to reductions in sexual risk even when results are negative.