We studied whether cardiac abnormalities contribute to the increased risk of stroke in patients with nonvalvular atrial fibrillation (NVAF). M-mode and 2D echocardiography were performed in four age- and gender-matched groups: 20 stroke patients with NVAF, 20 patients with NVAF who had not suffered a previous stroke, 20 stroke patients with sinus rhythm, and 40 healthy controls. Their mean age was 77 years. The two groups with atrial fibrillation differed from healthy controls in that they had more 2D-echocardiographic findings of severe left-ventricular-wall-motion abnormalities (p < 0.05) and tended more often to have enlarged left ventricles, and hypertrophic and congestive cardiomyopathy. Left atrial diameter was 47 mm compared to 41 and 39 mm in the two groups with sinus rhythm (p < 0.001). Intracardiac thrombi were only found in the two atrial-fibrillation groups (with stroke: 15% without stroke: 5%). Aortic sclerosis was common in all groups (30-60%), as was mitral annulus calcification (10-20%). The only significant difference between the two atrial-fibrillation groups was a higher frequency of earlier ischemic heart disease in the stroke group. Both atrial-fibrillation groups had cardiac abnormalities predisposing for embolic as well as thrombotic stroke.