Interruption of pregnancy is usually recommended for pregnant women with Eisenmenger's syndrome. We studied 13 pregnancies in 12 women with this syndrome, who decided to carry on with their pregnancy despite recommendation for therapeutic abortion. The mean age was 27 years. Five patients had ventricular septal defect; two, persistent ductus arteriosus; one, a combination of both; two, atrial septal defect; one, atrioventricular septal defect and one patient a combination of ventricular and atrial septal defects. Mean systolic and diastolic arterial pulmonary pressures were 112.7 and 61.7, mmHg, respectively. There were three spontaneous abortions, one premature labour at 23 weeks of gestation and two maternal deaths during the 23 and 27 weeks of gestation. Seven patients who reached the end of the second trimester were hospitalized until delivery and received heparin (20,000 to 40,000 units per day) and oxygen therapy. Caesarean section was performed in all patients as a result of worsening maternal or fetal clinical condition during the third trimester of gestation. all the mothers were discharged from hospital but one of them died on the 30th day post-partum. Five of the eight infants were premature, three were small babies for gestational age and all were discharged from hospital with the exception of one who died 48 h after birth. In conclusion, although pregnancy should be discouraged in women with Eisenmenger's syndrome, it can be successful. In this study, prolonged bed rest, the use of heparin and oxygen therapy presumably positively influenced maternal and infant outcomes.