The blood sugar content was determined in 142 patients with myocardial infarction on the 1--3rd, 7-10th, 28--30th days of the disease by the Hagedorn-Jensen method. The standard glucose tolerance test was conducted in 64 patients on the 30th day of the disease and repeated in 20 patients 18 months after infarction. It was concluded that transient hyperglycemia developed in 47.8% of patients with myocardial infarction in the acute period, predominantly in those with a sugar curve of the diabetes-decipiens type. Carbohydrate tolerance was reduced in two thirds of the patients. In some of them this disorder was attended with clinical signs of diabetes and a severe course of myocardial infarction. In patients with diminished carbohydrate tolerance the sugar curve remained abnormal 18 months after the disease. Obvious diabetes developed in 6 out of 20 patients examined. Among relatives of patients with disturbed carbohydrate metabolism diabetes mellitus was encountered more frequently and the incidence of ischemic heart disease and hypertension was higher.