The statistical observation was performed on 1,337 cases of premature babies over 5 gestational months delivered at the Maternity Hospital of Okayama University School of Medicine, during the period from April, 1934 to November, 1957. (total number of deliveries 10,000 during the same period). The following results were obtained from this observation. 1) The incidence of premature baby is 13.37%. (14.63≧P≧12.50%) 2) Being divided into two groups, prewar and postwar groups, there is noted the significant difference between them, the later showing the distinct decrease of the incidence. 3) The younger age group is generally higher than the elder in frequency. 4) There has been noted remarkable difference between the primiparous and the multiparous groups, the former having the higher frequency than the later. 5) The great majority of premature babies has been delivered in winter. 6) The ratio of male to female is 106 to 100. 7) The majority of babies is weighed over 2000g and beyond 253 days of fetal age. 8) The number of patients having historically the premature interruption of pregnacies is found more in the postwar than the prewar. 9) The types of labors are shown as follows, sponsaneous, 91.8%, breech presentation, 7.3%, and artificial induction of labors, 2.9%. (by bougie) 10) In about half number of babies, there are present the maternal complications to be suggestful as the causes, among which the great majority of number is covered by the premature rupture of membrane, toxemias of pregnancy, twin and contracted pelvis. 11) The external malformation is noted in 1.12%. 12) The death-rate of babies is 13.83% (15.99≧P≧12.38%) during 7 days of postpartum. Prewar: 12.31%, postwar; 17.27%. As has been shown above, the higher incidence has been noted in the postwar than prewar groups. The death-rate classified into the groups under the birth weight and the length of pregnacy has significant tendency. Dividing the death-rate mentioned above into the prewar and postwar groups, the later being not necessarilly increased in comparison with tha former. The remarkablly high deathrate is found at the time immediately after the delivery. The great majority of babies, being separated into the causes of death, was died of the congenital devility.