The aim of this study was to establish a connection between rheological disturbances and extensiveness of atherosclerotic changes in coronary angiogram. Patients were classified into two groups: group I--with multivascular atherosclerotic lesions (45 subjects at age of 58 +/- 11 years), group II--with univascular atherosclerotic lesions (18 subjects at age of 55 +/- 9 years). Blood samples were drawn from the cubital vein prior to the angiogram. Blood viscosity measurements were performed using low-shear Contraves viscometer-100 at 0.116; 1.0; 4.59 s-1 shear rates and Brokfield Cone/Plate Viscometer at 150 s-1. The plasma viscosity was measured by means of Ubbelohde's capilary viscometer. Besides the viscometric examinations the total cholesterol. LDL-cholesterol, HDL-cholesterol, triglycerides, glucose and fibrinogen as well as blood morphology and ESR were determined. All rheological measurements were carried out at the temperature of 37 degrees C immediately after blood drawing. The results of studies indicate that in patients with multivascular coronary disease whole blood viscosity at all examined shear rates was significantly greater then in univascular patients. It was found that the LDL-lipoproteins concentration was significantly elevated in the I group. Other examined parameters did not differ significantly. The examinations indicate that there exists the connection between hemorheological disturbances and the extensiveness of coronary heart disease.