In recent studies, it has been found that postmenopausal hormonal therapy is associated with an increased incidence of cardiovascular disease. Experimental studies suggest several potential mechanisms by which estrogens might decrease blood pressures, and estrogen administration attenuates hypertension in several animal models. In humans, although oral contraceptive agents are frequently associated with increases in blood pressure, blood pressure was not increased or was minimally increased in prospective clinical trials of hormone therapy in postmenopausal women. These observations suggest that the excess rates of cardiovascular disease are not caused by increased blood pressure.