The revolution in molecular genetics is contributing to the understanding of normal and abnormal cardiovascular development and morphogenesis. Recent investigations have shown that a growing number of congenital heart malformations is due to single gene defects. The combined contribution of clinical and molecular studies is providing the chromosomal map of the genes related to these isolated cardiac defects, and to syndromes characteristically associated with specific cardiac malformations. These advances are relevant to clinical practice, since the accumulated knowledge can improve the quality of management of affected patients.