Family studies throughout the 1970s and 1980s docu-mented the role of shared genetic factors in the familial aggregation of cardiovascular disease and its risk factors, including hypertension. These familial aggregation studies, however, do not identify and characterize the role of particular genes. Identification of the genes contributing to interindividual variation in disease risk may facilitate early identification of patients who are at elevated risk of cardiovascular disease before the onset of any clinical symptoms, development of more efficacious treatments by exploiting previously unidentified metabolic and physiological pathways, and the tailoring of particular treatments to patients who are most likely to respond on the basis of their genetic constitution.