Lack of standardized phenotypic definition has made outcome studies of Asperger syndrome (AS) difficult to interpret. This paper reports psychosocial functioning in 20 male adolescents with AS, defined according to current ICD-10 criteria, and a comparison group of 20 male adolescents with severe conduct disorder. Subjects were gathered from clinical referral. Evaluation used standardized interviewer rated assessments of social functioning and psychiatric morbidity. The AS group showed severe impairments in practical social functioning despite good cognitive ability and lack of significant early language delay. High levels of anxiety and obsessional disorders were found in AS; depression, suicidal ideation, tempers, and defiance in both groups. Results are compared with those from other studies. Relevance to clinical ascertainment and treatment is discussed.