Venous blood acid-soluble fraction was investigated by means of high-efficiency liquid chromatography in patients with myocardial infarction and angina pectoris. Myocardial ischemia is shown to result in marked changes of purine and pyrimidine metabolism. A rise in intermediate and end products of purine metabolism (inosine, hypoxanthine, xanthine, uric acid), and the emergence of thymin and thymidine were demonstrated in venous blood of patients with myocardial infarction and angina pectoris.