During an examination of a group of 63 patients with chronic ischaemic heart disease and condition after myocardial infarction the viscosities measured with the help of a rotation viscosimeter lay clearly above the values of good reference persons. There were positive correlations of the blood viscosity to the haematocrit value, fibrinogen level, globulin content as well as to the total protein, total lipid and cholesterol level. In the transition to the logarithm of the viscosity the measure for the linear dependence with the exception of the total protein level became smaller. A formation of partial correlation coefficients by means of the exclusion of the haematocrit in every case resulted in increasing coefficients r for the investigated parameters of the lipid metabolism cholesterol, total lipids and triglycerides.