In aortic valve replacement most centres prefer to use a mechanicalvalve for younger patients without special bleeding risks and treat thepatient with lifelong anticoagulation. However, a few patients do notreceive anticoagulation at all or have this withdrawn after some time. Weexamined the prognosis of 43 patients, 37 men and 6 women (mean age 52years), who were treated with anticoagulation for approximately only 1 year(mean 13 months; range 4-35 months) after isolated aortic valve replacementwith a mechanical valve. The mean follow-up period was 7 years and 3 months(1.5 months to 15 years and 10 months). After 5 and 10 years, 70% and 59%,respectively, were free of thromboembolic events, 65% and 55%,respectively, were free of valve-related events, and 87% and 83%,respectively, had survived. These figures correspond to linearized rates ofthromboembolic events of 5.2%/pt-yr, valve- related events of 6.2%/pt-yrand death of 2.9%/pt-yr. We conclude that the best postoperative treatmentin isolated aortic valve replacement with a mechanical valve is lifelonganticoagulation.