Fetal echocardiography. To determine the usefulness of prenatal echocardiography in the early diagnosis of congenital heart disease. All fetuses with suspected congenital heart disease referred to us between the years of 1988 and 1993 were reviewed. Prenatal echocardiograms and postnatal cardiac catheterization and surgery data were obtained from the medical records and analyzed with respect to diagnostic accuracy, timeliness of diagnosis, and impact on clinical management. For all patients, complete follow-up was possible. There were 33 fetuses who had echocardiography performed within 2 weeks of delivery, including 16 fetuses with pulmonary stenosis, 10 fetuses with critical pulmonary atresia, 2 fetuses with tetralogy of Fallot, and 5 fetuses with atrioventricular valve stenosis. The remainder had cardiomyopathy, endocardial fibroelastosis, arrhythmias, or structural anomalies. Echocardiography was initially successful in accurately identifying the specific type of heart disease in 91% of cases. There were no false-positive or false-negative diagnoses. Cardiac catheterization and surgical procedures were performed in a highly selected group of neonates who had significant hypoxemia with high pulmonary artery pressure. The echocardiograms were performed at a mean time of 32 weeks' gestation, with a range of 23-38 weeks. Echocardiography, performed with great care, is a safe, noninvasive, rapid, accurate method of evaluating suspected congenital heart disease in the fetus. It can be used as an initial screening method for congenital heart disease and to monitor fetuses whose pregnancies are at risk for congenital heart disease. The major impact of prenatal echocardiography is to initiate appropriate postnatal care to prevent neonatal mortality and chronic morbidity.