The variability in the individual response to drugs may be due either to interindividual variations in the pharmacokinetics of the drugs or to the heterogeneity of the mechanism(s) underlying the diseases, or both. In both cases, genetic heterogeneity is involved in the metabolism of cardiovascular drugs and pathogenesis of inherited cardiovascular disorders. Molecular genetic technologies can now provide sensitive and efficient genetic testing, not only to identify polymorphic drug metabolism genes, but also to identify disease-associated genes for diagnosis and risk stratification of many hereditary cardiovascular diseases. In this review, we discuss the polymorphic metabolism of cardiovascular drugs and the molecular genetics of cardiovascular diseases in relation to the genes determining the responsiveness to a given drug. (C) 2000 Elsevier Science Inc. All rights reserved.