Background. QT dispersion (QTd) represents the parameter of the expanded heterogeneity of myocard of ventricles. The aim of this study was to examine the dynamics of changes of QTd during the first 5 days of the acute myocardial infarction (AMI) in dependence to noninvasively estimated success of thrombolytic therapy. Methods. Thirty six patients with AMI were included in the study. All patients were treated with alteplaze according to rapid protocol. QTd (QTc max-QTc min) was measured immediately after the reception (0 min), after the thrombolytic therapy (90 min) and since the 2nd to the 5th day of the hospitalization. Reperfusion was estimated on the basis of electrocardiographic and biohumoral parameters. Results. In the group of 36 patients, 22 male and 11 female, both parameters of the reperfusion were not compatible in 3 patients. The other 23 patients had the reperfusion, while 10 patients did not have it. At the reception there was no significant difference of QTd between the group with reperfusion (79±34 ms) and the group without reperfusion (65±19 ms). After receiving alteplase, the average QTd in the group with reperfusion was 67±31 ms, which was not shorter in relation to the group without reperfusion (70±23 ms). Since the 2nd day of AMI, significantly smaller QTd in patients with reperfusion was not registered compared with the patients without the reperfusion (54±17 vs.73±20 ms), whereas since the 3rd day the difference became significant (46±16 vs. 87±24 ms). On the 4th day it was 43±12 vs. 78±21 ms, and on the 5th day it was 38±11 vs. 62±23 ms. On the 1st day significant difference of QTd between the groups with and without reperfusion was not registered in the group of patients with anterior AMI (0 min: 97±47 vs. 72±16; 90 min 68±47 vs. 72±20) whereas on the 2nd day it became statistically significant (51±15 vs. 74±20 on the 2nd day, 51±20 vs. 88±24 on the 3rd day, 46±10 vs. 81±19 on the 4th day and 40±8 vs. 69±22 ms on the 5th day. In the group of patients with inferolateral AMI, only on the 3rd day significant difference of QTd between the group with and the group without reperfusion was registered (43±14 vs. 69±29 ms), while in all other measuring it was not registered (0 min: 69±22 vs. 42±9; 90 min: 67±20 vs. 67±41; 55±19 vs. 60±25 on the 2nd day; 41±14 vs. 51±6 on the 4th day and 51±12 vs. 37±8 ms on the 5th day). Conclusion. Qt dispersion was of significantly shorter duration in patients with the successfully performed reperfusion in relation to the patients without the reperfusion. In patients with the anterior AMI, QTd was significantly different in patients with in relation to the patients without the reperfusion in distinction with the patients with inferolateral AMI.