Echocardiographic measurement of left ventricular mass has provided a way of evaluating the undesirable effects of high blood pressure on the heart in the same way as for obesity, excess salt intake and blood hyperviscosity. Recently, the left ventricular mass was shown to correlate (r = 0.81) with the hemodynamic stimuli of blood pressure, stroke volume and left ventricular contractility. Prospective trials at Cornell and Framingham indicate that left ventricular mass is a powerful predictive factor of the risk of complications in hypertension. In the first of these trials, we demonstrated in a 5 year follow-up study of 140 men with uncomplicated hypertension that the incidence of death, myocardial infarction or angina requiring myocardial revascularisation, was four times greater in patients with increased left ventricular mass and that this association was independent of the blood pressure levels. Then, in a 10 year follow-up study of hypertensive patients of both sexes, we established that the left ventricular mass was the most powerful predictive factor of mortality and morbidity and that this was so marked (15% death rate in subjects with LVH vs 1% in subjects with normal left ventricular mass--p less than 0.00001--, cardiovascular accidents in 26% of subjects with LVH compared with 12% in subjects with normal left ventricular mass--p less than 0.0001) that only left ventricular mass and age were independant predictive factors of morbid events in multiple variable analysis. In the Framingham study, the frequency of coronary events in a 4 year follow-up period of healthy subjects from the original cohort (average age 69 years) was significantly related to the left ventricular mass and independent of other risk factors.(ABSTRACT TRUNCATED AT 250 WORDS)