A group of 13 successfully treated hydrocephalic children living a normal social life according to their ages has been examined to evaluate the possible correlation between their brain size, intellectual development and physical disability. The brain size was assesed by ventriculography prior to initial surgery and by computer tomography (CT-scanning) at the time of investigation 6--11 years after operation. The intellectural development was evaluated by psychological investigation of the children and by evaluation of their social adaptation. The physical disability was investigated by neurological examination. Significant improvement in ventricular size was demonstrated from pneumoencephalographic examinations prior to surgery and to the CT investigations. No prediction of the intellectual development could be based on the ventriculographies prior to initial surgery. In spite of positive trends, correlation trends, correlation between the ventricular size as determined by CT-scans and the IQ was not significant, possibly due to the small number of cases available for study.