Asperger syndrome (AS) is a pervasive developmental disorder characterized by autistic social dysfunction and idiosyncratic interests in the presence of normal intelligence. There is no history of language delay. Although people with AS are known to suffer from comorbid psychiatric conditions, few studies have systematically addressed this topic. This preliminary report describes the occurrence of psychiatric disorders in a series of patients with AS diagnosed according to the ICD-10/DSM-IV criteria. Out of 35 patients (29 males and six females; mean age 15.1 years; mean verbal IQ 105.9; mean performance IQ 97.5; mean full-scale IQ 102.7), 23 patients (65%) presented with symptoms of an additional psychiatric disorder at the time of evaluation or during the 2-year follow-up. Children were most likely to suffer from attention deficit hyperactivity disorder, while depression was the most common diagnosis in adolescents and adults. The implications of these findings are discussed.