BACKGROUND: The use fixed-dose combination (FDC) is a critical tool in improving HAART. Studies on the effectiveness of combined lamivudine, stavudine and nevirapine (3TC/d4T/NVP) are scarce. OBJECTIVE: To analyse 6861 patients in a large observational cohort from 21 Médecins Sans Frontieres (MSF) HIV/AIDS programmes taking 3TC/d4T/NVP, with subcohort analyses of patients at 12 and 18 months of treatment. METHODS: Survival was analysed using Kaplan-Meier method and factors associated with progression to death with Cox proportional hazard ratio. RESULTS: Median baseline CD4 cell count at initiating of FDC was 89 cells/microl [interquartile range (IQR), 33-158]. The median follow-up time was 4.1 months (IQR, 1.9-7.3). The incidence rate of death during follow-up was 14.2/100 person-years [95% confidence interval (CI), 13.8-14.5]. Estimates of survival (excluding those lost to follow-up) were 0.93 (95% CI, 92-94) at 6 months (n = 2,231) and 0.90 (95% CI, 89-91) at 12 months (n = 472). Using a Cox model, the following factors were associated with death: male gender, symptomatic infection, body mass index < 18 kg/m and CD4 cell count 15-50 cells/microl or < 15 cells/microl. Subcohort analysis of 655 patients after 1 year of follow-up (M12 FDC cohort) revealed that 77% remained on HAART, 91% of these still on the FDC regimen; 5% discontinued the FDC because of drug intolerance. At 18 months, 77% of the patients remained on HAART. CONCLUSIONS: Positive outcomes for d4T/3TC/NVP are reported for up to 18 months in terms of efficacy and safety.