In a prospective study of perinatal losses associated with prediabetes, 105 pregnancies were followed in women showing mild abnormalities of glucose tolerance. Hypoglycemic agents were not administered in the absence of frank diabetes. All patients were attended at delivery by interns or residents. Only two perinatal losses (1.5%) occurred in complicated cases, one of which might have been avoided. Perinatal losses in unrecognized prediabetics are largely due to associated obstetric factors, and in uncomplicated prediabetes should not differ from nondiabetic pregnancies. Recognition of the prediabetic state allows subsequent complications to be anticipated and treated early. In the absence of frank diabetes, hypoglycemic agents would not improve the immediate fetal salvage. Their value for reducing the incidence of recognized complications or in promoting the remote welfare of the fetus (preventing the ultimate development of diabetes) has not been established. The administration of hypoglycemic agents to the pregnant prediabetic is not recommended in view of the possible teratogenic effect.