In sub-Saharan Africa, the position of efavirenz as a first-line nonnucleoside reverse transcriptase inhibitor remains to be discussed. We report here the 6-month efficacy and tolerance of an efavirenz-containing highly active antiretroviral therapy in a large cohort of HIV-1-infected adults. Seven hundred forty highly active antiretroviral therapy-naive adults (74% women; 14% with positive serum HBs antigen and 21% with abnormal baseline transaminase value) started zidovudine + lamivudine + efavirenz. At month 6, 1.2% of them were dead, 87% had undetectable viral load, and 7% had abnormal transaminase value. From months 1 to 6, the percentage of women who were actually using a contraceptive method increased from 58% to 80% (65% intramuscular progesterone and 35% oral estrogen/progesterone combination). The incidence of pregnancy was 2.6/100 woman-years (95% confidence interval, 0.67-4.51), and 86% of pregnant women voluntarily interrupted the pregnancy with no intervention on our part. Before month 6, only 0.8% of patients permanently discontinued efavirenz for severe adverse effects (neurologic, 0.6%; cutaneous, 0.1%; and hepatic, 0.1%). The leading cause of severe morbidity was tuberculosis. Considering the very high hepatic and cutaneous tolerance, efavirenz could be considered as a valuable first-line drug for women of childbearing age who agree to use contraception in sub-Saharan Africa, provided that the risk of teratogenicity should be closely monitored.