The left atrial spontaneous contrast is uncommon finding during transthoracic échocardiography. Transesophageal echocardiography provides superior imaging of the left atrium and left spontaneous contrast has been detected more frequently by this technique in rheumatic mitral stenosis. In order to analyze the significance of spontaneous contrast, we have studied 100 patients with mitral stenosis. Trans thoracic and transesophageal echocardiography were performed in all patients. Left atrial spontaneous echo contrast was detected in 60 patients (group A) and was absent in 40 patients (group B) The mean of mitral valvular area was 0.9 10.2 mm in group A and 48 9.5 mm in group B (p < 0.001). Ther was a high incidence of atrial fibrillation in group A; 63% VS 12% in group B (p < 0.001). A systemic embolization was noted in 20% of patients in group A; No one of group B has presented this complication (p < 0.001).