Background: Obsessive-compulsive disorder (OCD) is a relatively frequent disease in childhood, which is generally treated with selective serotonin reuptake inhibitors (SSRIs) and/or clomipramine and cognitive behavioral therapy (CBT). However, nearly half of the cases are treatment resistant. Aripiprazole was shown to be beneficial in augmentation therapy in treatment-refractory OCD. This study evaluated its effectiveness as a single agent in these cases. Methods: Sixteen children (nine girls, seven boys), who were nonresponders to treatment with at least two types of SSRIs and CBT, were administered 12 weeks of aripiprazole treatment with a mean dose of 4.75 mg/day (range: 2-7.5 mg/day). Treatment outcomes were evaluated by the Childhood Yale-Brown Obsessive Compulsive Scale (CY-BOCS), and the Clinical Global Impressions-Severity and Improvement (CGI-S and CGI-I) scales. Results: Children with a mean age of 10.9 +/- 2.9 years had severe obsessive compulsive symptoms at baseline, and >80% of them had another comorbid psychiatric disease. Significant improvements in symptoms were achieved after 12 weeks of aripiprazole treatment, which were evaluated by significant decreases in symptom scores in the CY-BOCS, and improvements in CGI-I scores. Conclusions: This very small study of aripiprazole, given to children with OCD resistant to at least 12 weeks treatment with at least two SSRIs and CBT, demonstrated striking improvement in CGI scores (all subsets, p <= 0.002) for 13 of 16 children, and halved all CY-BOCS subscores after similar to 12 weeks of treatment.