Objective: The determination of high risk patients for sudden death and sustained ventricular tachycardia after acute myocardial infarction constitutes the main goal to decrease morbidity and mortality. Every attempt that decreases the frequency of late potentials (LPs) on signal averaged ECG (SAECG) and corrected QT dispersion (QTc-d) may improve prognosis of patients. In this study, the effect of metoprolol on frequency of LPs and QTc-d was investigated. Methods: Thirty-five patients (mean age 53±9 years) with acute myocardial infarction who were not given thrombolytic therapy were enrolled. Patients in whom metoprolol was not administered formed group I (n=20) and patients who were given metoprolol constituted group II (n=15). Metoprolol was administered as an initial dose of 15 mg intravenously, following 6-8 hours 100 mg/d orally. To determine the frequency of LPs, SAECG records were performed on admission and at the end of the first week. At the same time, resting ECG recordings (12 leads, 50 mm/s) were obtained to calculate QTc-d. Variance analysis was used for statistical analysis. Results: In group I; frequency of LPs were found 30% on admission and at the end of the first week. In group II; frequency of LPs were 6% on admission and at the end of the first week there was no LPs. There was no statistically significant difference between two groups according to TQRS, RMS-40, LAS40 and QTc-d. Conclusion: Metoprolol decreases the frequency of LPs. It has no effect on cQT-d.