A retrospective study was conducted to assess the effectiveness and tolerability of atomoxetine in children and adolescents with pervasive developmental disorders (PDD). An outpatient clinic registry of individuals with PDD was used to identify all children and adolescents who received atomoxetine over a period of 12 months. Patients were included if concomitant medications remained unchanged. Treatment response was assessed using the Global Improvement item of the Clinical Global Impressions scale (CGI-GI) based on the Conners Parent Rating Scale (CPRS) routinely completed by primary caretakers and other clinical information available in the registry. Twenty patients were identified, including 16 males and 4 females (age, 11.5 years; standard deviation, 3.5). Most patients (80%) were taking at least 1 concomitant medication. Treatment dose was 43.3 mg (standard deviation, 18.1) and duration was 19.5 weeks (standard deviation, 10.5). Twelve patients were judged to be responders, as defined by a score of 1 or 2 on the CGI-GI. Differences between baseline and the end of the trial period were observed in the following CPRS subscales: Conduct, hyperactivity, inattention, and learning. No differences were noted in the anxiety and psychosomatic subscales. One patient discontinued atomoxetine because of severe mood swings. Atomoxetine may be beneficial for treating secondary symptoms of PDD, and prospective open-label or double-blind, placebo-controlled studies are needed to assess its efficacy and safety.