Clinical and cardiac catheterization data were collected from 39 infants with coarctation of the aorta and ventricular septal defect, 31 of whom were initially managed only by surgical repair of coarctation. Data were analyzed to determine mortality, morbidity, outcome and factors that might predict survival or the need for septal defect closure. Of the eight patients who did not require surgical treatment before 3 months of age, seven underwent coarctation repair alone at a mean age of 2.3 years. Of the 23 infants managed with coarctation repair alone, before age 3 months, 9 needed no additional surgical treatment and 6 required early and 8 required late repair of the ventricular septal defect. Seven infants underwent coarctation repair and simultaneous pulmonary artery banding and one eventually required debanding after spontaneous closure of the septal defect. The overall mortality rate in this series was 10.3% (mean follow-up time 5.7 years). Of 39 infants, 16 (41%) never required a second operation for ventricular septal defect closure. For patients who had only coarctation or coarctation repair with pulmonary artery banding at less than 3 months of age, ventricular septal defect size was categorized as small (less than 0.5 cm/m2), moderate (less than 1 cm/m2) or large (greater than 1 cm/m2) on the basis of defect size at operative repair or echocardiographic or angiographic assessment. Defect size did not necessarily correlate with the need for operative repair.(ABSTRACT TRUNCATED AT 250 WORDS)