The echocardiographic pattern of incomplete mitral leaflet closure (IMLC) is reported to be present in about 90% of patients with acute myocardial infarction and new onset of mitral regurgitation. To determine the significance of this echocardiographic sign, we retrieved all echocardiograms containing this abnormality from a file of 1200 consecutive echocardiograms. Seventy-three echocardiograms manifested IMLC. We also studied a control group consisting of 52 patients without IMLC, but who were matched with the IMLC group with respect to a range of left ventricular (LV) diameters at end diastole and fractional shortening. The following was found in the control group: fewer wall motion abnormalities per patient, less frequent mitral "B bumps," and a smaller LV end-diastolic dimension (LVEDD) (p less than 0.05 for each comparison). By logistic regression, the variable most important to the probability of having IMLC was the presence of mitral valve "B bumps." We conclude that: (1) elevated left ventricular filling pressure is associated with IMLC and (2) IMLC is not specific for the subset of patients with papillary muscle dysfunction due to acute myocardial infarction. Rather, IMLC is commonly seen in association with dilated, usually ischemic cardiomyopathy.