Forty-five severely handicapped patients were investigated on body temperature regulation. Poor regulation cases had CT scans showing severe third and lateral ventricle dilatation. Furthermore, in almost all poor regulation cases of perinatal and postnatal onset, CT scans showed extensive low density areas involving the frontal lobe. Electrophysiological studies (sSEP, ABR and blink reflex) could not show definite differences between poor regulation cases and good regulation cases. These findings suggest that hypothalamus, medial forebrain bundle and frontal lobe play important roles in body temperature regulation. On the other hand, perinatal or postnatal onset cases frequently had small body surface areas and low serum creatinine.