In a certain area of Szolnok county, 5,978 live births occurring in the period 1963-1965 were studied by the optimal epidemiological model. Of the study population, 5,433 children (91%), were identified. It was completed by 211 children, thus the total material involved 5,644 cases, and 67 congenital cardiovascular malformations were detected among them. Seven, being part of multiple congenital abnormalities, were excluded. Thus the birth prevalence of congenital cardiovascular malformations was 10.6 per 1000 live births.