The hemodynamic pattern of hypertrophied left ventricle in systemic hypertension was studied by M-mode echocardiography in 42 untreated hypertensive patients with left ventricular (LV) mass index greater than 2 standard deviations from the sex-specific mean of 114 normal subjects (normal values of our laboratory), and in 45 normotensive volunteers. Hypertensive patients showed cardiac dimensions, relative diastolic wall thickness, ratio of systolic pressure to end-systolic dimension, cardiac index and stroke index greater than normotensive control subjects (0.01 less than p less than 0.0001). Pressure/dimension ratio was correlated to relative wall thickness (p less than 0.005). End-systolic stress/volume ratio was normal as was systolic pressure to dimension ratio normalized for end-diastolic wall thickness. LV hypertrophy was concentric in 26% and eccentric in 74% of patients and suggested 2 different heart adaptations to overload: eccentric hypertrophy was associated with increased cardiac dimensions, high peak stress, normal systolic function and moderately increased LV contractility; concentric hypertrophy was associated with the highest blood pressure values, normal cardiac dimension, normal peak stress, normal systolic function and much increased LV contractility. Because stress/volume ratio and wall thickness-corrected systolic pressure/dimension ratio were normal in hypertensive patients, LV contractile capacity might be supported by the increase in myocardium available for contraction, rather than by increase in inotropic state.