In order to assess the sensitivity of the initial electrocardiogram (ECG) in diagnosing the first attack of acute myocardial infarction (AMI), we compared the findings on ECG and two-dimensional echocardiogram (2-D echo) in 74 patients with single vessel coronary artery disease. Group A consisted of 41 patients with infero-posterior AMI while group B consisted of 33 patients with antero-septal AMI. In group A, 12 patients showed normal ECGs, while 2-D echo failed to reveal abnormal left ventricular wall motion in only 2 patients. In those two patients, the quality of the echocardiogram was poor. In group B, only one patient showed a normal ECG, and all patients showed abnormal left ventricular wall motion on 2-D echo. We conclude that electrocardiography has limitations in diagnosing infero-posterior myocardial infarction especially during the acute phase, but 2-D echo is an additional useful diagnostic procedure.