Baseline data were collected in Cape Town during 2006 to study if patients on combination antiretroviral therapy (ART) experience decreased inhibition to avoid risky sexual behavior. A total of 924 HIV-positive individuals were recruited; 520 who initiated ART within 3 months and 404 waiting for ART. Nearly half of men (40.1%) and women (46.3%) reported having unprotected sex their last time. Men and women who did not disclose their HIV status to their partner [Odds ration (OR)=2.57 (95% CI: 1.22-5.50) and 2.84 (95% CI: 1.84-4.39), respectively], and those with ambivalent perception about the relationship between ART and HIV transmission [OR=2.08 (95% CI: 1.00-4.30) and 2.39 (95% CI: 1.50-3.84), respectively], were twice as likely to have had unprotected sex their last time. Results suggest an urgent need to strengthen prevention interventions among HIV-positive individuals on and about to start ART in this setting.