This study assessed the effectiveness and tolerability of the selective serotonin reuptake inhibitor citalopram in the treatment of patients with pervasive developmental disorders (PDDs). The medical charts of 15 children and adolescents (aged 6-16 yr) with Asperger syndrome, autism, or PDD not otherwise specified treated with citalopram were retrospectively reviewed. The final dose of citalopram was 16.9 +/- 12.1 mg/day with a treatment duration of 218.8 +/- 167.2 days. Independent ratings of the Clinical Global Impression (CGI) Severity and Improvement scales allowed comparison between baseline and PDD symptoms at the last visit. Eleven adolescents (73%) exhibited significant improvement in PDD, anxiety, or mood CGI score (z = 2.95; p =.003). Anxiety symptoms associated with PDDs improved significantly in 66% of patients (z = 2.83, p =.005), and mood symptoms improved significantly in 47% of patients (z = 2.78, p =.005). Mild side effects were reported by five patients (33%). These data suggest citalopram may be effective, safe, and well tolerated as part of the treatment of PDDs.