Sixty patients with essential hypertension and 51 patients with secondary hypertension were studied for evaluation of effects of hemodynamic and hormonal factors on development of left ventricular hypertrophy. The following methods were used: M-mode echocardiography, radiocardiography with I-131-albumin and radioimmunoassay of renin activity in peripheral blood plasma. Diastolic blood pressure was used for determination of a stage (I, II or III) of hypertension according to WHO recommendations. The character of changes of general and central hemodynamics and of activation of renin-angiotensin system was related to stage and clinical variant of hypertension. Correlation analysis showed that blood pressure was a primary determinant of development of left ventricular hypertrophy in patients with essential hypertension. Changes of cardiac output, circulating blood volume, and total peripheral resistance contributed to development of myocardial hypertrophy at later stages of the disease. In essential hypertension hormonal factor had no effect on development of left ventricular hypertrophy. In secondary hypertension development of left ventricular hypertrophy was determined by two main extracardiac mechanisms: hemodynamic on stages I and II, and hormonal operative on all stages of the disease.