Abstract In a retrospective study, the incidence of critical congenital heart disease in the State of Wisconsin was determined for the years 1969–1970. Two hundred sixty-two infants were identified in 5 pediatric cardiology centers giving an incidence of 1.7 cases per 1,000 live births. Patients were admitted to the study on the basis of cardiac catheterization (192), autopsy (53), or surgery without prior catheterization (17). Lesions most commonly encountered were ventricular septal defects (19 per cent), transposition of the great arteries (13 per cent), patent ductus arteriosus (11 per cent), hypoplastic left heart (10 per cent), and tetralogy of Fallot (9 per cent). Analysis was made to relate the specific cardiac anomaly to the age at which diagnostic and/or therapeutic intervention was required. One hundred nine surgical procedures were performed. These included: pulmonary artery banding (31), ligation of a PDA (24), systemic-to-pulmonary anastamoses (18), resection of aortic coarctation (8), and atrial septectomy (8). Survival rate of all surgical procedures was 71 per cent. At the end of 1 year of follow-up, 139 patients were alive (54 per cent). However, if patients who died without the opportunity for surgery or catheterization are excluded, survival rate was increased to 66 per cent.