In children with autism spectrum disorders, previous studies have shown high rates of psychiatric comorbidity. To date, studies on adults have been scarce. The aim of the present study was to investigate psychiatric comorbidity in young adults with Asperger syndrome. Participants were 26 men and 28 women (mean age 27 years) with a clinical diagnosis of Asperger syndrome. Psychiatric comorbidity was assessed by the Structured Clinical Interview for DSM-IV Axis I Disorders. IQ was measured using the Wechsler Adult Intelligence Scale, Third Edition. Autism spectrum diagnoses were confirmed using the Diagnostic Interview for Social and Communication Disorders. In our study group, 70% had experienced at least one episode of major depression, and 50% had suffered from recurrent depressive episodes. Anxiety disorders were seen in about 50%. Psychotic disorders and substance-induced disorders were uncommon. In conclusion, young adults with autism spectrum disorders are at high risk for mood and anxiety disorders. To identify these conditions and offer treatment, elevated vigilance is needed in clinical practice. (Contains 3 tables.)