Thirty-one delinquent male children who were also hyperactive were compared with 35 male delinquents who were not hyperactive. Data was gathered through parental interviews and from school, pregnancy, and birth records. The hyperactive delinquents had a lower birth weight than their brothers and than nonhyperactive delinquents, and possibly more delivery and postnatal complications than the nonhyperactive group. In addition, their antisocial behavior showed an earlier onset. The symptoms 'reckless and irresponsible,' 'fighting,' and 'drug abuse' were significantly more common among the hyperactives. The two groups did not differ in socioeconomic status, IQ, school performance prior to the onset of antisocial behavior, number of broken homes, and frequency of parental mental illness (including alcoholism). The finding that the families of the hyperactives were not disadvantaged when compared to the families of the nonhyperactives provides support for the hypothesis that the pregnancy and birth complications -- primarily low birth weight -- may be etiologically linked to the hyperactivity. More research in this area is recommended. Related studies are reviewed. Data are presented in tabular form, and a reference list of 28 items is included. (Author abstract modified.)