Congenital malformations of the heart are the most common of all birth defects. Traditionally, a multifactorial model combining genetic predisposition with environmental influence has been cited as the cause of greater than 90% of heart disease. This may be too broad inasmuch as linkage analysis combined with the explosion of information derived from the Human Genome Project has allowed the identification of genetic defects for many types of acquired and congenital diseases of the heart. This review provides a summary of cardiac conditions for which genetic etiologies are apparent, as well as an introduction to some basic clinical genetic concepts. Despite significant advances, it is important to remember that we are still very early in our understanding of the relationship of genotype to phenotype and that the clinical implications of the genetic defects identified are incompletely understood and have only begun to be studied.