Left ventricular aneurysms after myocardial infarction are generally considered one of the complications of severe coronary artery disease. Postinfarction ventricular aneurysms with normal coronary arteriogram are rare. Only a few cases have been reported previously in Japan. We examined the incidence and the clinical characteristics of postinfarction ventricular aneurysms without coronary obstruction. Among the consecutive 1800 patients studied in our laboratory with selective coronary cineangiography and left ventriography, we found 5 (4 male, 1 female) patients with left ventricular aneurysms with no or minimal coronary arterial obstruction. The patient's ages ranged from 34 to 83 with a mean of 59. Interestingly, no patient had prior anginal history, and every case occurred with a first sudden attack of chest pain. The likely mechanisms causing the development of myocardial infarction were coronary spasm and/or thromboembolic accident. One patient, in whom a coronary induction test was performed, showed positive findings. It is possible that poor collateral circulation and well preserved contraction of viable myocardium in these patients bring about the formation of left ventricular aneurysm after myocardial infarction with normal coronary arteriogram.