The short-term efficacy and tolerability of sertraline for adults with pervasive developmental disorders (PDDs) were assessed in this investigation. Forty-two adults with PDDs (autistic disorder, N = 22; Asperger's disorder, N = 6; and PDD not otherwise specified [NOS], N = 14) participated in a 12-week, open-label, systematic trial of sertraline. Behavioral ratings of repetitive symptoms, aggression, and social relatedness were obtained at baseline and after 4, 8, and 12 weeks of sertraline administration. Twenty-four (57%) of 42 patients showed significant improvement, primarily in repetitive and aggressive symptoms. Statistically significant changes in measures of social relatedness did not occur. Patients with autistic disorder and PDD NOS did significantly better than those with Asperger's disorder. Based on global improvement item criteria from the Clinical Global Impression Scale, 15 of 22 (68%) patients with autistic disorder, none of six (0%) patients with Asperger's disorder, and 9 of 14 (64%) patients with PDD NOS were categorized as treatment responders. Sertraline was well tolerated; no adverse cardiovascular effects, extrapyramidal symptoms, or seizures were identified. These findings suggested that sertraline may be an effective treatment for interfering repetitive and aggressive symptoms in adults with PDDs. Definitive statements about the efficacy and tolerability of sertraline for treating adults with PDDs must await results from double-blind, placebo-controlled trials. These preliminary results should not be generalized to include children and adolescents with PDDs.