It is well known that various types of hemorrhage in the newborn account for a considerable percentage of stillbirths and neonatal deaths. Bundesen and others1 reported that there were 237 deaths from intracranial hemorrhage among 2,260 neonatal deaths in 1936 and 1937. In an endeavor to decrease the percentage of stillbirths and to decrease mortality and maldevelopment in the newborn, we have studied the effect of vitamin K administered in various ways to women in labor or administered directly to the newborn. In a previous article2 we reviewed the history of vitamin K and appended an extensive bibliography. The cases cited in that article are included in this report. The methods of determining the prothrombin were the same for the whole series, namely a modification of the Smith bedside technic for determinations on maternal and cord blood and the micro method of Kato and Poncher for determinations on