Investigations of the effects on the people who had received placental exposure at either Hiroshima or Nagasaki were discussed. All of the subjects were children who had been born at either Hiroshima or Nagasaki between noon of 31, May, 1946 and the atomic-bomb detornation. Deaths of embryos and neonates were determined by the radiation dosage and the growth phase of embryos. Bifid uvula and a slight decrease of number of lumbar vertebra were observed in 14 males and 3 females at Nagasaki. Mental deficiency occurred in 25% of the children whose mothers had received radiation at Nagasaki, and in 8% at Hiroshima. The occurrence of microcephaly was high at both places in the children who had received placental exposure of more than 150 rad. A significant retardation of growth was observed in those who had had a high radiation dosage. Congenitally abnormal persistence of pupillary membrane was very frequently observed in the group which had received a high dosage of radiation. Concerning progeria, mortality of infants under one year of age was increased in the group which had received a high dosage of radiation, but mortality statistics should continue to be observed.