The weak relation of systolic blood pressure to left ventricular mass in hypertensive patients is often interpreted as evidence of nonhemodynamic stimuli to muscle growth. To test the hypothesis that left ventricular chamber size, reflecting hemodynamic volume load and myocardial contractility, influences the development of left ventricular hypertrophy in hypertension, we studied actual and theoretic relations of left ventricular mass to left ventricular diastolic chamber volume, pressure and volume load, and an index of contractility. Data were obtained from independently measured M-mode and two-dimensional echocardiograms in 50 normal subjects and 50 untreated patients with essential hypertension. Two indices of overall left ventricular load were assessed: total load (systolic blood pressure x left ventricular endocardial surface area) and peak meridional force (systolic blood pressure x left ventricular cross sectional area). A theoretically optimal left ventricular mass, allowing each subject to achieve mean normal peak stress, was calculated as a function of systolic blood pressure and M-mode left ventricular end-diastolic diameter. Left ventricular mass measured by M-mode echo correlated better with two-dimensional echocardiogram derived left ventricular end-diastolic volume (r = 0.56, p less than 0.001) than with systolic blood pressure (r = 0.45, p less than 0.001) and best with total load or peak meridional force (r = 0.68 and 0.70, p less than 0.001). In multivariate analysis both end-diastolic volume and blood pressure were independent predictors of systolic mass (p less than 0.001) and explained most of its variability (R = 0.75, p less than 0.001). Theoretically optimal left ventricular mass was more closely related to end-diastolic volume (r = 0.72, p less than 0.001) than to systolic blood pressure (r = 0.46, p less than 0.001); thus, the relatively weak correlation between blood pressure and optimal mass reflected the influence of left ventricular cavity size, rather than a lack of proportionality between load and hypertrophy. Actual and theoretically optimal left ventricular mass were closely related (r = 0.76, p less than 0.001), indicating that left ventricular hypertrophy in most cases paralleled hemodynamic load. Left ventricular mass was positively related to stroke index and inversely to contractility (as estimated by the end-systolic stress/volume index ratio), the main determinants of left ventricular chamber volume. In multivariate analysis, systolic blood pressure, stroke index, and the end-systolic stress/volume index ratio were each independently related to left ventricular mass index (all p less than 0.001, multiple R = 0.81) and accounted for 66% of its overall variability.(ABSTRACT TRUNCATED AT 400 WORDS)