Both echocardiography and radionuclide angiography have been proposed as noninvasive modalities for the diagnosis of left ventricular pseudoaneurysm. In the only three cases seen at our institution over the past five years, this diagnosis was missed with radionuclide blood pool imaging, while two-dimensional echocardiography demonstrated the typical features of a pseudoaneurysm. Our patients were asymptomatic and diagnosis was made incidentally 4 to 6 years after myocardial infarction. Although the patients survived an extended period without surgery, the reported incidence of rupture is high, and prophylactic surgical repair probably is indicated. It is likely that the increased use of noninvasive cardiac imaging techniques will lead to the detection of other cases of unsuspected left ventricular pseudoaneurysm. Two-dimensional echocardiography appears superior to planar radionuclide ventriculography in establishing the diagnosis.