Erythrocyte deformability (ED), blood and plasma viscosity and other parameters such as haematocrit, haemoglobin, fibrinogen and blood protein levels are the main determinants of the rheological properties of the blood. We have assessed these properties in 24 individuals with a history of myocardial infarction and stable angina pectoris and in 20 healthy volunteers. ED, blood and plasma viscosity, fibrinogen, erythrocyte sedimentation rate, haemoglobin, haematocrit, thrombocyte, cholesterol, triglyceride, and low density lipoprotein (LDL)-cholesterol levels were significantly higher in the study group than in the control group. Also there were significant correlations between the following parameters: blood viscosity (BV) and fibrinogen; blood viscosity and haematocrit; plasma viscosity (PV) and fibrinogen; plasma viscosity and haematocrit; blood viscosity and erythrocyte sedimentation rate (ESR); blood viscosity and thrombocyte count; and ED and cholesterol, tryglyceride and mean corpuscular volume (MCV). Med Sci Res 27:327-329 (C) 1999 Lippincott Williams & Wilkins.