Objective: Atomoxetine's tolerance and efficacy were studied in 24 patients with pervasive developmental disorder and symptoms of ADHD. Method: Prospective, open-label, 16-week study was performed, using the variables of the Clinical Global Impression Scale and the Conners' Scale, among others. Results: A significant difference was found between pre- and posttreatment scores as well as a significant reduction was found on the scales used. Only five patients presented adverse events. Conclusion: Atomoxetine therefore appears to be a useful drug, pointing to the need for larger, randomized, controlled, double-blind studies to confirm its efficacy versus placebo and in comparison with other treatment options. (Contains 4 figures and 2 tables.)