Due to its long half-life (25-30 hours) the once daily administration of nevirapine would appear logical but we do not have data regarding the tolerability and efficacy of this schedule. We have therefore tried to evaluate this schedule in 93 HIV-infected patients beginning a treatment containing nevirapine. The tolerability of once daily nevirapine was similar to the usual schedule with 15% of mucocutaneous allergy. The immunologic and virologic efficacy of once daily nevirapine was confirmed with a mean RNA HIV decrease of 1.4 log, 1.3 log, 1.1 log and 1.3 log at M1, M3, M6 and M9 respectively. The best results were observed in naïve patients. Residual plasma concentration of nevirapine was performed in 35 patients with a mean value of 3.8 mg/l.