The youths were tested for physical, psychiatric, intellectual, academic, perceptual, and motor functioning. The results showed that the youths showed impairment in many of the areas tested. Learning disabilities, personality disorders, and conduct disorders were very common. No relationship between neuropsychological impairment and family background or social performance was found. The paper discusses implications of these findings for understanding and treating delinquents. Tables, footnotes, and about 40 references are included. (Author abstract modified)