OBJECTIVES: To assess the clinical features, pathologic findings, postoperative results and the effects of immunosuppressive therapy in patients with Behçet's disease (BD). METHODS: We reviewed the postoperative course of the 9 BD patients who underwent a total of 17 aortic valve replacement procedures with prosthetic valves. RESULTS: Histological examination of the aortic valve commonly revealed diffuse myxoid degeneration (75 percent). Of 17 valve replacement surgeries, 13 surgeries resulted in complications, such as detachment of the prosthetic valve with perivalvular leakage and dehiscence of the sternotomy wound, within an average of 5 months (range from 1 month to 14 months). The rate of prosthetic valve detachment was 76 percent (13 of 17 surgeries). Four of the 9 patients (44 percent) who underwent aortic valve replacement procedures died of heart failure or infection associated with the detachment of the prosthetic valve, and perivalvular leakage within an average of 9 months. Aortic insufficiency associated with dehiscence of the prosthetic valve developed in 11 of 12 surgical cases (92 percent) with a mechanical valve and 2 of 5 surgical cases (40 percent) with tissue valves. Thirteen of 15 surgeries (87 percent) which were not given postoperative immunosuppressive therapy developed complications, while none of 2 surgeries that used postoperative immunosuppressive therapy with prednisolone (1 mg/kg/day) and azathioprine (100 mg/day) had these complications. CONCLUSION: The rates of prosthetic valve detachment in BD involving aortic valve were higher than those of other diseases. Aortic valve involvement was also one of the poor prognostic factors in BD. Intensive postoperative immunosuppressive therapy and surgical methods may be important factors for postoperative results.