Two additional cases of successfully managed Eisenmenger's syndrome (ES) during pregnancy are described. A review of the literature on this subject revealed 115 reported cases, of which only 44 (including our two cases) were felt to be adequately documented, representing 70 pregnancies. These formed the material for statistical evaluation. Fifty-two per cent of all patients died in connection with pregnancy. Thirty and three-tenths per cent of all pregnancies results in maternal death. Maternal mortality in first, second, and third pregnancies was not significantly different. A high incidence of maternal death was assoicated with hypovolemia, thromboembolic phenomena and preeclampsia, but mortality was not higher in the toxemia than in the non-toxemia group. Cesarean sections and other operations are associated with extremely high maternal mortality during pregnancy. Thirty-four per cent of all vaginal deliveries, three out of four cesarean sections, and only 1 out of 14 pregnancy interruptions (the only one by hysterotomy) resulted in maternal death. Abortions are significantly safer than any kind of delivery (p less than 0.05). Ventricular septal defect (VSD) is the most frequent underlying shunt defect. Maternal mortality in association with VSD is higher (60%) than in association with atrial septal defect (ASD) (44%) and patent ductus arteriosus (PDA) (41.7%). The majority of maternal deaths occurred during or within the first week after delivery. Only 25.6 per cent of all pregnancies reached term. At least 54.9 per cent of all deliveries occurred prematurely. Thirty and two-tenths per cent of all infants showed intrauterine growth retardation. This represented almost half of all new borns with available information. Perinatal mortality reached 28.3 per cent and was significantly associated with prematurity (p less than 0.001). Pregnancy is contraindicated in patients with ES. Abortion is the treatment of choice, once pregnancy has occurred. Where interruption of pregnancy is refused, utmost care must be taken to assure maternal and fetal survival. A protocol for the management of such pregnancies is discussed on the basis of available information.