The aim of the study was the evaluation of the QT dispersion interval in patients with acute myocardial infarction, taking into consideration its location, treatment provided and coronary artery reperfusion. Investigations were performed in 75 patients treated because of acute myocardial infarction, including 57 men and 18 women, age 40-84 years. Acute myocardial infarction was recognised on a base of generally accepted criteria. At the reception standard 12-outputs ECG was performed. Next ECG testing was performed after 3 hours from the start of the thrombolytic therapy. In case of patients which were not qualified for thrombolytic therapy next ECG was applied within 3 hours after reception. For further observation of changes in QT dispersion ECG generally provided within 2, 3, 4 and 5 day of hospitalization were used. Taking as a location criterium of infarction the method of provided treatment and obtained reperfusion in the infarcted area, patients were classified to the one of 6 groups. To the first group (I)-patients with inferior wall infarction, treated thrombolytically with obtained reperfusion-15 patients were included, age 41-69 years. To the second group (II)-patients with inferior wall infarction, treated thrombolytically without obtained reperfusion-18 persons were included, age 43-84 years. To the third group (III)-patients with inferior wall infarction, not treated thrombolytically-9 patients were included, age 49-72 years. To the fourth group (IV)-patients with anterior wall infarction, treated thrombolytically with obtained reperfusion-9 persons were included, age 40-73 years. To the fifth group (V)-patients with anterior wall infarction, treated thrombolytically without obtained reperfusion-10 persons were included, age 47-78 years. To the sixth group (VI)-patients with anterior wall infarction, not treated thrombolytically-14 patients were included, age 44-81 years. Control group for the comparison of initial evaluation of the QT and QTc dispersion interval was group of 11 healthy persons, age 27-64 years. There was proved, that in patients with acute myocardial infarction, independently of its location, QT and QTc dispersion was increased. Thrombolytic therapy in patients with acute inferior wall myocardial infarction with reperfusion obtained causes extension of QT dispersion. In patients with acute anterior wall myocardial infarction thrombolytic therapy with obtained reperfusion causes reduction of QT and QTc dispersion. In patients not treated thrombolytically, which had anterior wall myocardial infarction, in first days of observation QT and QTc dispersion was increased. This effect was not observed in patients with inferior wall infarction.