The study consists of two parts: the first presents the data of clinical and statistical analysis of 153 patients with acute myocardial infarction who have been observed during one year, 12,6 % had concomitant diabetes mellitus. According to the clinical and statistical analysis, high mortality rate during one year follow-up in patients with diabetes mellitus was determined. The second part presents clinical and functional parameters of the 38 patients with acute myocardial infarction, 22 of them had concomitant diabetes. On the 12–15th days of myocardial infarction echocardiography and bicycle exercise test were performed. There were no significant differences of the majority of the studied indices in patients with or without diabetes mellitus in acute phase of the disease. Such results may be explained by more severe disturbances caused by myocardial infarction. The additive influence of diabetes mellitus on clinical course of the postinfarction period needs further investigations with prolonged observation.