We compared blood viscosity at a high and a low shear rate, hematocrit, as well as levels of fibrinogen, cholesterol, triglyceride and high density lipoprotein-cholesterol between 42 patients with nonembolic cerebral infarction and 39 normal subjects. Blood viscosity, levels of fibrinogen, cholesterol and triglyceride were significantly higher, and high density lipoprotein-cholesterol levels were significantly lower, in patients than in normal persons. Blood viscosity had a positive correlation with hematocrit and fibrinogen, and a negative correlation with high density lipoprotein-cholesterol, but no correlation with cholesterol and triglyceride.