OBJECTIVE: To evaluate adherence, treatment interruptions, and outcomes in patients purchasing antiretroviral fixed-dose combination (FDC) therapy. DESIGN: Ninety-seven participants were recruited into a prospective 24-week observational cohort study of HIV-positive, antiretroviral-naive individuals initiating self-pay Triomune or Maxivir therapy in Kampala, Uganda. Adherence was measured by monthly structured interview, unannounced home pill count, and electronic medication monitors (EMM). Treatment interruptions were measured as continuous intervals greater than 48 h without opening the EMM. The primary outcomes were survival with viral suppression below 400 copies/ml, CD4 cell increases, and genotypic drug resistance at 24 weeks. RESULTS: The median baseline CD4 cell count was 56 cells/microl and median log10 copies RNA/ml was 5.54; mean adherence ranged from 82 to 95% for all measures but declined significantly over time. In an intent-to-treat analysis, 70 (72%) patients had an undetectable plasma HIV-RNA level at week 24. Sixty-two of 95 (65%) individuals with continuous EMM data had a treatment interruption of greater than 48 h. Treatment interruptions accounted for 90% of missed doses. None of 33 participants who did not interrupt treatment for over 48 h had drug resistance, whereas eight of 62 (13%) participants who did interrupt therapy experienced drug resistance. Antiretroviral resistance was seen in 8% of individuals and overall mortality was 10% at 24 weeks. CONCLUSION: HIV-positive individuals purchasing generic FDC antiretroviral therapy have high rates of adherence and viral suppression, low rates of antiretroviral resistance, and robust CD4 cell responses. Adherence is an important predictor of survival with full viral suppression. Treatment interruptions are an important predictor of drug resistance.