The frequency of chromosomal abnormalities in infants with congenital heart disease has been estimated from postnatal clinic data to be 5% to 10%. Over an 18-month period we performed fetal echocardiograms on 502 fetuses and found cardiac anomalies in 34. Eleven of these fetuses (32%) had abnormal chromosomes. This marked discrepancy from the data found in the pediatric literature may relate to nonviable fetuses identified in utero, who escape pediatric case identification. We conclude that in cases of fetal heart disease the workup should include either amniocentesis or fetal blood sampling for chromosome analysis. The information can be used for complete parental counseling and for managing delivery and neonatal care.