Examined with over 28,000 7-year-old children whose mothers registered for prenatal care was the relationship between perinatal complications and such characteristics as poor school achievement, hyperactivity, and neurological soft signs associated with the diagnosis of minimal brain dysfunction (MBD). Ten perinatal antecedents were studied: toxemia, fever, cigarette smoking during pregnancy, placental complications, use of mid forceps, breech delivery, low birthweight, diagnoses of neonatal brain abnormality and dysmaturity, and significant respiratory events. (Tables provide statistical data regarding the frenquencies of MBD symptoms with each of the above perinatal conditions.) (SBH)