In 41 patients with different types of cardiomyopathy (19 congestive = COCM, 6 hypertrophic obstructive = HOCM, and 16 hypertrophic non-obstructive = HCM) ventricular enddiastolic volume (EDV), endsystolic volume (ESV), and ejection fraction (EF) were determined angiographically and values of both ventricles were compared. In the mean, volume parameters increased significantly and EF of both ventricles decreased as compared to control values of patients with coronary heart disease without myocardial infarction. In COCM volume parameters reached pathologic values as in the total patient group whereas in HOCM and in HCM values did not differ significantly from control. Left ventricular function was reduced more often and, in the mean, more severely than right ventricular function. This became evident e.g. from the incidence of enddiastolic volume increase and the course of the regression line. A similar finding can be derived from the reversal of the normal relation of volume parameters of both ventricles. Only in rare cases right ventricular function was more severely impaired than left ventricular function. These findings indicate a simultaneous impairment of both ventricles in cardiomyopathy. The more pronounced left ventricular function disturbance may be attributed to the higher left ventricular work load. Thus, left ventricular biopsies might be of greater diagnostic significance than right ventricular biopsies.