Background: In acute myocardial infarction, ST segment elevation in the electrocardiogram obtained on presentation is often accompanied by ST depression. Debate on the importance of this reciprocal ST depression continues. Objective: To study the value of reciprocal ST segment depression during early exercise ECG in patients presented with acute myocardial infarction and received thrombolytic therapy. Patients and Methods: Fifty patients who received intravenous thrombolytic therapy for acute myocardial infarction were subjected to the following:- - Full history taking, thorough clinical examination, and 12 leads surface ECG, exercise ECG, echocardiography and coronary angiography. Patients were classified into three groups according to exercise test results: - Group I without ST segment change. - GrQup H with isolated ST segment depression. - Group HI with reciprocal ST segment depression. Results: There was no significant difference between the three groups as regard age, sex, hypertension, hypercholesterolemia, diabetes mellitus and the occurrence of reciprocal ST segment depression during exercise. Chest pain during exercise was significantly higher in patients with isolated ST segment depression and was lower in those either with reciprocal or without ST segment depression Wall motion abnormalities were less in patients with reciprocal ST depression, but without statistically significant difference. Left ventricular ejection fraction was lower in patients with reciprocal ST depression. The reciprocal ST depression during exercise was significantly associated with single vessel disease and with persistent occlusion of the artery related to infarction. Conclusion and recommendations: Reciprocal ST segment depression that occurred during early exercise stress testing in patients with acute myocardial infarction who were treated by thrombolytic therapy is most probably due to a passive electrical phenomenon and not due to remote ischemia. The performance of this study in a large number of patients using all possible new diagnostic modalities and extending the scale of the study to include patients late after myocardial infarction should be done.