Maternal conditions leading to the premature delivery of infants have been studied by a number of clinicians, and we have summarized their conclusions, which have differed widely, in a previous communication.1 In the majority of these studies the incidence of these conditions in the mothers of mature infants has not been compared with the incidence in mothers of immature infants. Furthermore, the few excellent reviews in which control groups were employed depended on retrospective surveys, that is, on the analysis of observations which were not deliberately planned for the purpose of the study. In attempting to obviate some of the errors which might occur in studies of this kind, we have interviewed all of the mothers who entered the obstetric wards of the Cincinnati General Hospital during the period of one year in order to compare, under similar conditions, the histories of mothers who bore immature infants with the