Among 1436 patients who underwent valve replacement, the 400 first cases were studied to assess the features of recurrent systemic embolic event. The mean follow-up was 87 months. Three groups of patients were compared: group A — 289 patients without any thromboembolic event (72·25%); group B—78 patients with only one embolic event (19·5%); group C—33 patients with several embolic events (8·25%). The frequency of recurrence was high: one patient out oj three (linearized mean 8·9% in group C considering only one recurrence, vs 3·8% in group B). The recurrence have the same location in 45% of patients. The consequences of these embolisms are serious: each event has a 30 to 40% risk of death or major disability. Four variables seem statistically to promote the occurrence of embolic events: mitral prostheses, pre-operative fibrillation, left atrial enlargement, poor anticoagulant therapy. 54 months after the first embolic event, 60% of the patients with poor anticoagulant therapy experience a recurrent thromboembolism vs 20% with adequate therapy. Twenty-six patients of groups B and C had a pathological study of prostheses. Thrombosis of the prostheses was found in 12 out of 18 patients in group B and in 7 out of 8 patients; in group C. Strict observance of anticoagulant therapy is the better way to prevent thromboembolism and especially recurrences. A reoperation is sometimes necessary. Valve re-replacement was performed in 27 cases out of 1436 patients.