Background: Angina occurs when there is regional myocardial ischemia causedby inadequate coronary perfusion and is usually but not alwaysinduced by increases in myocardial oxygen requirements. Objective: The aim of this work was to study the significance of ST changes in aVR, V5, V1 during exercise ECG for diagnosis of single -or multi-vessel coronary artery disease. Patients and methods: This study had been carried out in the cardiology department, Zagazig University and National Hear Institute during the period from January 2005 to January 2007. This study included 56 patients (40 male +16 female) with chronic stable angina. Results: Comparison was done among groups regarding demographic data, resting ECG data, echocardiographic findings and there were no statistical significant difference among groups. Single vessel disease: LAD: - the ability of the test to detect left anterior descending (LAD) lesion as a single vessel disease has high specificity 87.5%, high +ve predictive value 96%, but low sensitivity 50%. Left circumflex (LCx): the sensitivity of the test to detect LCx lesion as a single vessel disease was 53.4%, specificity 60%, but with low +ve predictive value 44%. RCA: as regard RCA lesion the test has low sensitivity, specificity positive and negative predictive values. Conclusion: The concomitant appearance of exercise-induced ST-segment elevation in lead V1 and in lead aVR with simultaneous ST-segment depression in lead V5, or the isolated appearance of ST-segment elevation in lead V1 mostly detects single-vessel disease and correlates strongly with significant narrowing of the LAD coronary artery as single-vessel disease, or with significant stenosis of the LAD and LCx coronary arteries as double-vessel disease.