From the changing incidence of cerebral palsy (CP) in the Tottori joint study, the absolute number of saved non-CP babies in the period 1955-1984 in the whole of Japan was calculated as about 33,000. The significant decrease of the incidence in the period 1955-1980 was mainly related to the advances made in perinatal medicine. In contrast, the recent reincrease is attributable to low-birth-weight CP. As for the risk factors for quadriplegia or double hemiplegia of CP, maternal toxemia, low Apgar scores and neonatal abnormal signs were important. Diplegia and paraplegia were significantly correlated with low birth weight. Among the babies weighing below 2,000 g, there was a more than 40-fold increased risk of CP compared with that in the general population. As for the risk for low-birth-weight diplegic CP, the number of abnormal signs in the neonatal period is correlated with the brain damage. The next step in preventing perinatal brain damage might be to give more attention to fetal deprivation and to well-balanced and sensible neonatal care of risk babies.