Left ventricular (LV) pseudoaneurysms form when cardiac rupture is contained by adherent pericardium or scar tissue. Although LV pseudoaneurysms are not common, the diagnosis is difficult and they are prone to rupture. We evaluated the clinical presentation, diagnostic accuracy of imaging modalities, results of therapy and prognosis of 290 patients with LV pseudoaneurysms. Most cases of LV pseudoaneurysm were related to myocardial infarction (particularly inferior wall myocardial infarction) and cardiac surgery. Congestive heart failure, chest pain and dyspnea were the most frequently reported symptoms, but >10% of patients were asymptomatic. Physical examination revealed a murmur in 70% of patients. Almost all patients had electrocardiographic abnormalities, but these were usually nonspecific ST segment changes; only 20% of patients had ST segment elevation. Although radiographic findings were also usually nonspecific, the appearance of a mass was present in more than one half of patients and may be an important clue to the correct diagnosis. Left ventricular angiography was the most definitive test and can be useful in planning surgery since concomitant coronary angiography can be performed. Regardless of treatment, patients with LV pseudoaneurysms had a high mortality rate, especially those who did not undergo surgery. Because the symptoms, signs, electrocardiographic abnormalities and radiographic findings seen in patients with LV pseudoaneurysms can be indistinguishable from those in patients with coronary disease alone, a high clinical index of suspicion is needed to avoid missing the diagnosis.