Antecedents of minimal brain dysfunction were investigated by examining the association of three major symptoms--learning difficulties, hyperkinetic-impulsive behavior, and neurological soft signs--with socioeconomic, perinatal, developmental, and familial variables. A major report describing the project was published in 1981. Learning difficulties were related to low socioeconomic status and tended to run in families; the familial association was likely determined environmentally. Preschool predictors were more strongly related to hyperkinetic-impulsive behavior than were early antecedents. Also implicated however, were genetics, demographic factors, pregnancy complications, and infant development. Both hyperkinetic-impulsive behavior and neurological soft signs were more highly related to preschool performance than to perinatal complications. Altogether more than 350 significant associations between the three MBD symptoms and antecedent variables were found. The identification of many of these antecedents, for example, family configuration, maternal smoking, and specific physical abnormalities will be useful in the formation of etiological hypotheses and in programs of prevention and treatments.