OBJECTIVE This study was conducted to clarify the significance of abnormal Q-wave regression in anterior wall acute myocardial infarction. METHODS A total of 74 patients who presented with a first anterior wall acute myocardial infarction within 6 h of onset were divided into two groups according to the presence (group A, n = 29) or absence (group B, n = 45) of regression of abnormal Q waves. Regression of abnormal Q waves was defined as the disappearance of the Q wave and the reappearance of the r wave > or = 0.1 mV in at least one of leads I, aVL, and V1 to V6. RESULTS Emergency coronary arteriography revealed that group A had a higher incidence of spontaneous recanalization or good collateral circulation than group B (55% vs 31%, P < 0.05). Peak creatine kinase activity tended to be lower in group A than in group B (2358 +/- 1796 vs 3092 +/- 1946 IU.L-1, P = 0.09). Group A had a greater left ventricular ejection fraction and better regional wall motion at 1 and 6 months after acute myocardial infarction than group B. The degree of improvement of left ventricular ejection fraction and regional wall motion between 1 and 6 months after acute myocardial infarction was significantly greater in group A than in group B. CONCLUSIONS Patients with anterior wall acute myocardial infarction showing Q-wave regression had a trend towards a smaller amount of necrotic myocardium and a significantly larger amount of stunned myocardium.