The study describes the changes in basic hemodynamic parameters after long-term antihypertensive therapy with cilazapril - a new ACE inhibitor lacking a sulfhydryl group - in hypertensive patients and the drug effects on renal function, glucose tolerance and lipid metabolism. 30 patients (18 males, 12 females, mean age: 53.3 ± 18 years) with mild to moderate essential hypertension were studied. The following determinations were performed in patients, before and after 4.5 months of cilazapril monotherapy at a dose of 5 mg/24 h: (a) antihypertensive action of the drug (arterial pressure at rest and during a 24-hour recording); drug effects on left ventricular (LV) mass index; its contractility indexes (%FS, EF) and the left atrial emptying index were studied by means of echocardiography; plasma insulin concentration during oral glucose tolerance tests, in the fasting state, after the administration of 75 g glucose per os, as well as the changes in the insulinogenic index and the 6-keto-PGF<sub>1α</sub>/TXB<sub>2</sub> ratio, and drug effect on renal function (urea, creatinine, uric acid, plasma electrolytes), blood lipid profile (total cholesterol, triglycerides, HDL-CH) and serum transaminases. Long-term drug administration exhibits an effective antihypertensive action, without causing reflex tachycardia and also reduces the LV mass index without affecting its EF, while improving its diastolic function. It does not significantly affect the various biochemical parameters, and achieves glucose regulation, both in the fasting state and after glucose loading, with a decrease in the insulinogenic index, and simultaneously increases the 6-keto-PGF<sub>1α</sub>/TXB<sub>2</sub> ratio. The existence of a direct cause-effect relationship between the changes in the above hormone systems is possible.