The aim of this study was to provide guidelines for optimal anticoagulation in Chinese patients after mechanical heart valve replacement. A Carbomedics valve was implanted in 178 patients between July 2000 and July 2003. During follow-up, 22 bleeding events and 1 thromboembolic complication occurred. The linearized rates of bleeding and thromboembolism were 5.83% and 0.26% per patient-year, respectively. The linearized mortality rate was 0.79% per patient-year. The final mean international normalized ratio (INR) was 1.68+/-0.38, however there was a significant variation between the early and late periods of follow-up. For Chinese patients with mechanical heart valves, bleeding was the major complication rather than thromboembolism. Low-dose anticoagulation (international normalized ratio 1.4-2.0) could markedly decrease bleeding and effectively prevent thromboembolism. As the INR was most unstable in the first postoperative month, re-examination of patients in this period is critical.