Of 35 infants who underwent an operation for coarctation of the aorta, 15 did not undergo cardiac catheterization before surgery. The diagnoses in all uncatheterized patients were made by clinical examination, chest radiography, ECG, and two-dimensional echocardiography combined with pulsed Doppler echocardiography. Associated anomalies diagnosed by two-dimensional/Doppler echocardiography included a patent ductus arteriosus in all patients, bicuspid aortic valve in six, small ventricular septal defect in four, and complete common atrioventricular canal in one. In no instance was the diagnosis of coarctation in error. In addition, the clinical significance of the ventricular septal defect was judged correctly by two-dimensional echocardiography, and no patient required an early reoperation because of significant left-to-right shunt. Two significant lesions were missed in one patient each: mitral stenosis and aortic stenosis. These diagnoses were missed in patients who were first seen with either profound congestive heart failure or shock. Coarctation of the aorta and associated lesions can be diagnosed accurately by two-dimensional echocardiography. This permits proper patient management without the added risk of cardiac catheterization. Although mitral and aortic lesions may be missed because of low cardiac output, this does not result in management errors.