BACKGROUND Persistent ST segment elevation in anterior myocardial infarction was classically attributed to ventricular aneurysm. This association is now considered controversial. To contribute to the elucidation of the problem, the association of this electrocardiographical finding with left ventricular aneurysm and function was assessed. METHODS In the catheterization studies of 85 patients with chronic anterior wall myocardial infarction the left ventricular function (ejection fraction) and the possible presence of ventricular aneurysm were investigated. These findings were correlated with the persistence of ST segment elevation. RESULTS 56 of the 85 patients (66%) had persistent ST segment elevation, and 29 (34%) had isoelectric ST segment. 32 cases of left ventricular aneurysm were detected in the group with elevated ST segment (57%) and none in the group with isoelectric ST segment. The ejection fraction was markedly depressed in the group with elevated ST segment (0.34 +/- 0.13) in contrast with the group with isoelectric ST segment (0.52 +/- 0.11) (p less than 0.001). This abnormality in ventricular function was independent from the presence or absence of aneurysm (ejection fraction 0.34 +/- 0.12 vs 0.35 +/- 0.14). CONCLUSIONS The persistent ST segment elevation is associated with a greater left ventricular function depression, independently from the presence of aneurysm, which is a common finding and exclusive of the group with persistently elevated ST segment.