Aim To investigate the clinical significance of reciprocal ST-segment changes during acute myocardial infarction. Methods The clinical and electrocardiographic data were analyzed and compared with results of coronary angiography in 166 patients with first acute myocardial infarction (AMI). Results Compared with the patients without precordial ST- segment change, the level of creatine kinase, the incidence of arrhythmia and heart failure as the complications of acute myocardial infarction and the percentage of lesions in left anterior descending artery (LAD) and multiple coronary vessels were significantly higher, the level of left ventricular ejection fraction was significantly lower in patients with precordial V 4～V 6 ST-segment depression during inferior acute myocardial infarction. On the other hand, the incidence of proximal lesion in LAD as the infarct-related artery was significantly higher in patients with inferior ST-segment depression than those without in anterior acute myocardial infarction, whereas the creatine kinase level, left ventricular ejection fraction and incidence of acute myocardial infarction complication were not significantly different between the two groups. Conclusions Precordial V 4～V 6 ST- segment depression during early inferior acute myocardial infarction may indicate larger inferior infarct, or accompanying disease of LAD or multiple coronary vessels. Anterior acute myocardial infarction complicated inferior ST-segment depression may suggest proximal lesion in LAD, which is an indication for early reperfusion therapy.