The medical records of 102 live-born children with a congenital diaphragmatic defect were reviewed to determine the frequency and nature of underlying chromosomal, genetic, and nongenetic patterns of malformation. Overall, 40 children (39%) had a major nonpulmonary malformation, and 14 of these children (14%) had a previously recognized pattern of malformation. A group of 18 children (18%) with cardiac anomalies had an increased mortality rate in comparison with those children without cardiac defects (72% vs 38%). The frequency and severity of nonpulmonary abnormalities in children with congenital diaphragmatic defects suggest that examination of affected children should include cardiac evaluation, a karyotype when the defect is one feature of a broader pattern of altered development, and a careful evaluation for minor anomalies, which may provide clues to an overall diagnosis.