4,409 children born in Bohemia (1974-1983) with heart defect were distributed almost between 2,296 (52.1%) boys and 2,213 (47.9%) girls: The boy:girl ratio was 1.09:1. Boys prevailed in double outlet right ventricle (2.68:1), hypoplastic left heart (2.25:1), transposition of the great arteries (2.11:1), aortic stenosis (1.95:1), pulmonary atresia (1.55:1), tricuspid atresia (1.45:1), coarctation of the aorta (1.30:1) and the corrected transposition (1.25:1). Girls prevailed significantly in patent ductus arterious (1.66:1), Ebstein's anomaly of the tricuspid valve (1.57:1), truncus arterious (1.22:1), atrioventricular septal defect (1.17:1) and tetralogy of Fallot (1.12:1). The difference in the remaining heart defects was less than 10%.