Poisoning or intoxication is the occurrence of harmful effects resulting from exposure to a foreign substance. According to the Center for Disease Control, approximately 1 million of the 110 million annual emergency department (ED) visits are related to poisoning and other toxic effects. Electrocardiogram (ECG) is a noninvasive, relatively inexpensive diagnostic test that provides important information regarding not only the heart, but also non-cardiac events impacting the cardiac system. The aim of this study was to evaluate the electrocardiographic changes conducted on 282 cases of acute poisoning admitted to Tanta Poison Center, Faculty of Medicine, Tanta Emergency University Hospital during the period from the start of July - 2009 to the end of June - 2010. In order to fulfill this aim, each patient was subjected to history taking, complete physical examination, laboratory investigations and ECG analysis. This study found that poisons associated with ECG changes account for 58.5 % of patients included in this study. Furthermore, 36.17% of patients are mainly in the middle age group between 20 and 30 years. Organophosphorus compounds (34.4%) were responsible for most cases of intoxication of ECG changes. Sinus tachycardia (73.94%) was the commonest ECG change among them. Followed by prolonged QT corrected for heart rate (QTc) interval (21.82 %) and sinus bradycardia (11.51 %).