Blood pressure is controlled by a complex combination of processes that influence cardiac output and peripheral vascular resistance. Multiple genes potentially influence each parameter involved in the control of blood pressure, and individuals with the same blood pressor level do not necessarily have the same genotype at relevant loci, nor do individuals with the same genotype at particular loci necessarily have the same blood pressure. Nevertheless, pharmacogenetic studies of vascular reactivity will certainly allow the analysis of the mechanisms affected by genes, and lead to a better understanding of the epidemiologic observations seen in large groups of patients. Polymorphisms in the genes of the renin-angiotensin system allow definition of the "genetic profile" associated with a higher risk of cardiovascular disease, and can also be linked to significant changes in vascular reactivity in arteries isolated from patients carrying the polymorphisms.