To evaluate the usefulness of echocardiographic regional wall motion abnormalities (RWMA) in detecting coronary artery disease (CAD) in patients with left ventricular (LV) dysfunction and a normal-sized or dilated left ventricle, 103 patients were studied by two-dimensional echocardiography (2DE) and cardiac catheterization. In 60 patients (group I) who had LV dysfunction and a dilated left ventricle by echo (patients with dilated cardiomyopathy), RWMA were detected in 44 patients and 38 (86%) of them had significant CAD, usually two- or three-vessel obstruction; of the 16 patients with dilated cardiomyopathy (DCM) and diffuse LV hypokinesis, eight (50%) had evidence of CAD. Thus the presence of RWMA by 2DE had an 83% sensitivity, a 57% specificity, and a 77% predictive accuracy in detecting CAD in patients with DCM and thus in distinguishing ischemic from idiopathic DCM. In 43 patients with LV dysfunction but normal LV size (group II), the sensitivity, specificity, and predictive accuracy of RWMA in detecting significant CAD was 95%, 100%, and 95%, respectively. We conclude that the detection of RWMA by 2DE is highly suggestive of significant CAD in patients with LV dysfunction and normal-sized or dilated left ventricle; the finding, however, of diffuse LV hypokinesis does not exclude CAD in these patients, especially when the left ventricle is dilated.