The influence of delivery in breech presentation on the occurrence of minimal brain dysfunction (MBD) has been studied. Parents of 8--15 year old children were asked to account for behavioral and educational deficits and needs of their children from birth until the date of investigation. It was found that among prematurely delivered children, the frequency of MBD, defined as hyperkinesia and learning disability, amounted to about 20 per cent and was similarly distributed between children , however, the average frequency of hyperkinesia and learning disability amounted to 8 per cent; in children born in breech presentation it was 14 per cent, while in those born in vertex presentation the corresponding figure was 2 per cent. MBD was more common in boys (16 per cent) than in girls (12 per cent).