The association between left atrial spontaneous echo contrast (SEC) and a history of systemic arterial embolization was evaluated in 359 consecutive patients with rheumatic mitral valve disease during a 3-year period. All patients underwent transesophageal echocardiographic (TEE) and cardiac catheterization studies. Of these, 207 patients had predominant mitral stenosis, 55 had significant mitral regurgitation, and the remaining 97 with xenograft mitral valve replacement developed valvular dysfunction (32 resulted in predominant mitral stenosis and 65 in significant mitral regurgitation). Left atrial SEC was detected in 108 patients (group A) and was absent in 251 (group B). Group A patients showed a higher frequency of left atrial thrombi or history of previous embolization than those in group B (59.3% vs 7.2%; p < 0.001). Group A patients also had a higher frequency of recent (< or = 1 week before TEE study) and remote (> 1 week before TEE study) embolization than did group B patients (recent: 19.4% vs 2.8% [p < 0.001]; remote: 13.0% vs 4.0% [p < 0.001]). Multivariate analysis showed that left atrial SEC (p = 0.01) was the only independent predictor of systemic arterial embolization. It is concluded that patients with left atrial SEC had a significantly higher risk for thromboembolism, and TEE is a useful modality to identify this subset of patients with rheumatic mitral valve disease.