To test whether left ventricular aneurysm independently influences survival after acute myocardial infarction, a series of 386 consecutive men aged 60 years or less, were followed up for 57 (40-100) months. Catheterization was performed 1 month following the infarct. Aneurysm, defined as a diastolic outward bulging with akinetic or dyskinetic systolic motion, was diagnosed in 52 patients (13.5%). Mortality was higher (29% vs 14%; P less than 0.02) in patients with left ventricular aneurysm; their probability of survival at 60 months was 75% vs 90% in patients without aneurysm. Cox regression analysis for the whole population identified ejection fraction, bifascicular block, number of diseased vessels and angina after infarction as the only independent predictors of survival; when adjusted for these variables, differences in mortality between patients with and without aneurysm were no longer significant. To investigate further the role of aneurysm in survival, the 52 patients presenting with left ventricular aneurysm were matched with 52 of the remaining 334 patients according to the following baseline variables: ejection fraction, number of diseased vessels, left ventricular end-diastolic pressure, and bifascicular block. The survival curves of these two subsets were similar (mortality rates of 75% and 82%, respectively). Cox regression analysis of the whole cohort of 104 patients selected bifascicular block and the number of diseased vessels, but not left ventricular aneurysm, as independent predictors of outcome.