In this study, the effect of the angiotensin-converting-enzyme inhibitor (ACE inhibitor) Ramipril (5 mg/day) and calcium antagonist Isradipin (5 mg/day) treatment of two groups of hypertensive patients (n = 22 in each of group) was evaluated. The parameters of the hemorheological profile (blood and plasma viscosity, red blood cell aggregation and deformation, plasma protein concentration and its osmolality, hematocrit and ratio of Hct/blood viscosity) were measured in basal conditions (before treatment) and after 3 weeks of treatment. The patients showed some increased blood, plasma viscosity, RBC aggregability and fibrinogen concentration in basal conditions. In both groups of patients, three main parameters of the hemorheological profile (plasma viscosity, Hct and RBC aggregation) decreased after treatment. No significant changes in red cell deformability was found. In conclusion, ACE inhibition with Ramipril and calcium channel blocking with Isradipin lead to a moderate improvement of blood rheology in patients with hypertension. This may be explained by the pronounced vasodilatatory effect of ACE inhibitor and calcium antagonist, though their acting mechanism is different.