BackgroundHIV spread continues at high rates from infected persons to their sexual partners. In 2009, an estimated 2.6 million new infections occurred globally. People living with HIV (PLHIV) receiving treatment are in contact with health workers and therefore exposed to prevention messages. By contrast, PLHIV not receiving ART often fall outside the ambit of prevention programs. There is little information on their sexual risk behaviors. This study in Mombasa Kenya therefore explored sexual behaviors of PLHIV not receiving any HIV treatment.ResultsUsing modified targeted snowball sampling, 698 PLHIV were recruited through community health workers and HIV-positive peer counsellors. Of the 59.2% sexually-active PLHIV, 24.5% reported multiple sexual partners. Of all sexual partners, 10.2% were HIV negative, while 74.5% were of unknown HIV status. Overall, unprotected sex occurred in 52% of sexual partnerships; notably with 32% of HIV-negative partners and 54% of partners of unknown HIV status in the last 6 months. Multivariate analysis, controlling for intra-client clustering, showed non-disclosure of HIV status (AOR: 2.38, 95%CI: 1.47-3.84, p < 0.001); experiencing moderate levels of perceived stigma (AOR: 2.94, 95%CI: 1.50-5.75, p = 0.002); and believing condoms reduce sexual pleasure (AOR: 2.81, 95%CI: 1.60-4.91, p < 0.001) were independently associated with unsafe sex. Unsafe sex was also higher in those using contraceptive methods other than condoms (AOR: 5.47, 95%CI: 2.57-11.65, p < 0.001); or no method (AOR: 3.99, 95%CI: 2.06-7.75, p < 0.001), compared to condom users.ConclusionsHigh-risk sexual behaviors are common among PLHIV not accessing treatment services, raising the risk of HIV transmission to discordant partners. This population can be identified and reached in the community. Prevention programs need to urgently bring this population into the ambit of prevention and care services. Moreover, beginning HIV treatment earlier might assist in bringing this group into contact with providers and HIV prevention services, and in reducing risk behaviors.