Commonly used psychotropic drugs have unwanted side effects, most importantly on the cardiovascular system. In these study electrocardiographic changes induced by psychiatric drugs was assessed, with the special focus on QT prolongation and QT dispersion, which are important markers of sudden cardiac death. Two electrocardiograms have been obtained in admission and one week after hospitalization from 74 patients in psychiatric ward of Taleghani Hospital (in Tehran, Iran). ECG variables have been analyzed and compared. Max-QTc was increased in both sexes from 9.6% at admission to 28.8% during hospitalization. QT dispersion (equal or more than 50ms) increased from 43% in admission to 52.1% in the same time period. In women, we found a statistical correlation between drug treatment and QTc prolongation. In men, despite increased absolute QTc, this amount was statistically insignificant. By considering all types of drug treatment, an increase in QTc or dispersion was discerned, even though statistically, insignificant. A significant statistical relation ship was detected between QT prolongation and using methadone, beta-blockers, advanced age and hypocalcemia. Max and Min QTc and QT dispersion revealed a statistically significant incre-ment on second tracing. Hence, it’s advocated in patients treated with QT prolongating drugs, particularly in the presence of other risk factors, periodic electrocardiographic control during a treatment period to carry out.