During a 3.5 yr period 94 latently and manifestly diabetic patients were treated in the State Maternity Hospital of Helsinki. Management of manifestly diabetic patients included strict control of maternal glucose metabolism based on plasma glucose values after meals and on fasting plasma glucose values, early hospitalization and delivery near term to avoid infant morbidity due to prematurity. Fetal surveillance was based primarily on daily nonstress fetal heart rate monitoring and frequent urinary estriol determinations. Hypertensive disorders were encountered in 33% of patients in class A and 24% of patients in classes B through F; urinary tract infections were found in 17% and repeated maternal hypoglycemic episodes were found in 20% of manifestly diabetic mothers. Diabetic retinopathy showed variable progression during pregnancy in 50% of cases and was unchanged in the remaining 50%; only 16% of patients with hypertensive retinopathy showed progression on reexamination. The perinatal mortality was 1.1%. Delivery by cesarean section was performed in 55.3% of cases. The duration of gestation at the moment of delivery was 38.9 wk in class A and progressively less in classes B through F according to the severity of the diabetic disorder. The following percentages reflecting infant morbidity were encountered: respiratory distress syndrome, 5.3%; neonatal hypoglycemia, 10.6%, hyperbilirubinemia, 8.5%; hypocalcemia, 5.3% and the aspiration syndrome, 5.3%. Two infants had congenital anomalies: 1 had hyposadias and the other had aortic coarctation.