To determine the impact of 2-dimensional (2-D) and Doppler echocardiography on the care of children aged 2 years and younger with suspected cardiac disease, the clinical management and outcome for the years 1975 (pre-2-D/Doppler era, 161 patients) and 1985 (2-D/Doppler era, 206 patients) were compared. Differences were: (1) decreased catheterization at our institution (48% vs 21%, p less than 0.0001); (2) trend toward decreased recatheterization of patients with referral catheterization (62% vs 38%, p = 0.08); (3) increased operation without preoperative catheterization (10% vs 37%, p less than 0.001); and (4) decreased preoperative catheterization for 7 anomalies (patent ductus arteriosus, ventricular septal defect, atrial septal defect, atrioventricular canal, aortic stenosis, tetralogy of Fallot and complete transposition of great arteries). Operative mortality rates were not statistically different in the years compared. Also, the operative mortality rates in 1985 for patients with and without preoperative catheterization were not statistically different. In 1975, cardiac catheterization changed the primary clinical diagnosis in 21%. In 1985, the primary diagnosis was not changed by catheterization; however, 2-D and Doppler echocardiography changed the diagnosis in 18%. The change in utilization of cardiac catheterization appears to be most closely related to the maximal utilization of a substitute imaging and hemodynamic modality--namely, 2-D and Doppler echocardiography.