All children with a critical heart disease in a 6.3 million inhabitants territory were referred and all infants who died were autopsied and the protocols sent to the only Center of Pediatric Cardiology and Cardiovascular Surgery. In the first 5 years of the centralized care, 1,122 infants, i.e. 2.36/1,000 live births suffered from a critical heart disease. 639 (57%) were admitted to the Center and the rest died in provincial hospitals with but not always from a heart disease found at autopsy. An additional 43 (6.2%) patients had nonstructural heart disease and 12 (1.7%) had heart diseases not considered to be critical. The total incidence of critical heart disease fluctuated from 2.15 to 2.51/1,000 live births without any well-defined trend. A decrease in the relative frequency throughout the 5-year period was found for common arterial trunk, pulmonary stenosis and atresia while an increase was observed in patency of the arterial duct. The most frequent critical heart diseases in infancy were: ventricular septal defect (18.2%) - mostly in isolation; complete transposition (14.6%); aortic coarctation (10.0%); hypoplastic left heart syndrome (9.1%) and pulmonary atresia (6.3%). The majority (51.4%) of patients became critically ill or died in the neonatal period. The most common conditions seen in neonates were complete transposition (22.5%), hypoplastic left heart syndrome (16.1%) and coarctation of the aorta (9.5%). The highest share of critically ill patients was encountered in complete transposition (100%), pulmonary atresia (98.7%), common arterial trunk (97.4%) and double outlet right ventricle (92.1%). The least dangerous were atrial septal defect (6.6%), pulmonary stenosis (7.0%), aortic stenosis (12.2%) and ventricular septal defect (21.0%). The mean age was 76 (+/- 56) days at admission and 59 (+/- 73) days at death. Urgent cardiovascular surgery was performed in 235 (36.8%) of the 639 patients admitted in infancy, that is 0.5 per 1,000 live born children.