Left ventricular hypertrophy (LVH) has assumed an important role in clinical medicine as a result of the clinical implications of this often asymptomatic finding. Epidemiological data from the Framingham Heart Study have permitted an examination of prevalence, incidence, underlying predisposing factors and prognosis of LVH. Although LVH is an infrequent finding on the electrocardiogram, it is a forerunner of coronary disease, congestive heart failure, stroke and even peripheral arterial disease. Despite being strongly related to hypertension, LVH remains associated with excess risk for adverse cardiovascular morbid and fatal outcomes, even after adjusting for blood pressure. The risks associated with LVH are comparable with those of myocardial infarction. The recent introduction of echocardiography at the Framingham Heart Study has permitted the development of new criteria for LVH based on M-mode determined left ventricular mass. Unlike its electrocardiographic counterpart, echocardiographically determined LVH is a common finding, occurring in over 15% of the general population. Echocardiographic LVH is related to hypertension, obesity, valvular heart disease, coronary disease and advancing age. Ambulatory ECG results in subjects with echocardiographic LVH demonstrate increased risk for ventricular arrhythmias, which have been shown in other clinical settings to predict risk for sudden cardiac death. Preliminary data from Framingham and elsewhere suggest that echocardiographic LVH is associated with increased risk for cardiovascular disease morbidity and all-cause mortality.