This Grand Rounds is concerned with the classification of Asperger's syndrome and its continuity/discontinuity with autism. Information on a 15-year-old with the condition is presented as are data on other family members. The proband exhibited a longstanding pattern of marked deficits in social interaction, motor awkwardness, and unusual, circumscribed interest consistent with a diagnosis of Asperger's syndrome. Both the proband and his father exhibited unusual discrepancies between verbal and performance (nonverbal) cognitive abilities favoring the former. Deficits were observed in the social use of language. Father and son had similar abnormalities on magnetic resonance imaging examination. Potential differences between higher-functioning autism and Asperger's syndrome are important areas for future research.