Congenital heart diseases are starting to benefit from the major advances provided by the advent of molecular biology methods. It is now possible to identify genes which are responsible for congenital heart diseases. The gene responsible for supravalvular aortic stenosis--an autosomal dominant trait--was cloned last year. It is the elastin gene. DiGeorge and Shprintzen syndromes, conotruncal anomaly face and some cardiac malformations have a common cause: a deletion of the 22q11 region resulting in a monosomy. Although the region of deletion is large, it is possible that monosomy of only one gene results in these conditions. Studies are underway to evaluate the impact of this new genetic factor on the incidence of congenital heart malformations. Studies on familial bundle branch block, and lateralization defect with midline anomalies are soon going to show a chromosomal region with the gene defect. Discovering the genes and their protein products which are implied in the cardiac morphogenesis will definitively change our understanding of these cardiac malformations.