BACKGROUND We evaluated the efficacy, safety and tolerability of etravirine in paediatric patients vertically infected with HIV-1. METHODS A multicentre retrospective study of 23 multidrug-resistant paediatric patients (five children and 18 adolescents) enrolled in the study from 1 September 2007 to 28 February 2010 was carried out. We performed a longitudinal analysis of immunological, virological and clinical data. RESULTS The median age of the patients was 14.2 years [interquartile range (IQR) 12.5-15.8 years]. At baseline, the median HIV-1 RNA was 29 000 (4.5 log(10) ) HIV-1 RNA copies/mL (range 4300-83 000 copies/mL), the median CD4 T-cell count was 445 cells/μL (range 221-655 cells/μL) and the median CD4 percentage was 19.6% (IQR 13.0-31.0). Remarkably, 16 of 23 patients (70%) harboured one or more etravirine-associated resistance mutations. The backbone regimen included at least two fully active drugs in 91% of patients. After etravirine-based therapy, 20 patients (87%) achieved HIV-1 RNA<400 copies/mL and 18 of 23 (78%) achieved HIV-1 RNA<50 copies/mL: three (13%) within the first month, seven (30%) within the first 4 months, and six (26%) between the 5th and 8th months. CD4 T-cell recovery was observed in 19 patients (83%). The median follow-up time was 48.4 weeks (IQR 35.7-63.4 weeks); four patients (17%) were exposed to etravirine for >120 weeks. Three mild/short-term and two moderate skin rashes were observed in the adolescents. Laboratory abnormalities included hypercholesterolaemia (11 of 23 patients), hypertriglyceridaemia (eight of 23 patients), and reduced high-density lipoprotein cholesterol (10 of 23 patients). Adherence was complete in seven patients (30%). No patients showed complete resistance to etravirine after follow-up. However, three of 21 patients (14%) who initially showed intermediate resistance interrupted etravirine treatment because of virological failure. CONCLUSIONS We observed a sustained antiviral response and improved immunological parameters in multidrug-resistant paediatric patients, most of whom had received etravirine as part of salvage regimens with at least two fully active drugs.