The aim of this study was to assess efficacy of aripiprazole augmentation of serotonin reuptake inhibitor (SRI) treatment in adolescents with obsessive-compulsive disorder (OCD) who did not respond to 2 initial trials with SRI monotherapy. A consecutive series of 39 adolescents (28 males and 11 females; age range, 12 to 18 years; mean age, 14.6 ± 1.2 years), with OCD diagnosed based on a clinical interview and according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria, were included. The mean final aripiprazole dosage was 12.2 ± 3.4 mg/d. At the endpoint, 27 patients (59.0%) had a Clinical Global Impression (CGI)-Improvement score 1 or 2 (very much or much improved) and a Clinical Global Impression-Severity (CGI-S) score 3 or below and were thus considered responders. The CGI-S improved from 6.0 ± 0.9 at the baseline (severely to extremely severely ill) to 3.5 ± 1.0 (mild to moderately ill) at the end of the follow-up (P < 0.0001), whereas the Children's Global Assessment Scale improved from 39.2 ± 5.8 to 49.8 ± 9.0 (P < 0.0001). Compared with nonresponders, responders were less impaired at the baseline in functional impairment (Children's Global Assessment Scale; P = 0.004) but not in clinical severity (CGI-S). Subtypes of OCD comorbidity and absence of insight did not affect clinical response. Mild transitory agitation (10.3%), mild sedation (10.3%), and sleep disorders (7.7%) were reported, but any of the patients discontinued medication because of adverse effects.In these severely impaired adolescents, aripiprazole augmentation of SRIs was well tolerated and effective in more than half of the patients.