Background. It remains unknown whether there is any important clinical advantage to the use of either a bioprosthetic or mechanical valve for patients with native or prosthetic valve endocarditis. Methods. Between 1964 and 1995, 306 patients underwent valve replacement for left-sided native (209 patients) or prosthetic (97 patients) valve endocarditis. Mechanical valves were implanted in 65 patients, bioprostheses in 221 patients, and homografts in 20 patients. Results. Operative mortality was 18 ± 2% and was independent of replacement valve type (p > 0.74). Long-term survival was superior for patients with native valve endocarditis (44 ± 5% at 20 years) compared with those with prosthetic valve endocarditis (16 ± 7% at 20 years) (p < 0.003). Survival was independent of valve type (p > 0.27). The long-term freedom from reoperation for patients who received a biologic valve who were younger than 60 years of age was low (51 ± 5% at 10 years, 19 ± 6% at 15 years). For patients older than 60 years, however, freedom from reoperation with a biological valve (84 ± 7% at 15 years) was similar to that for all patients with mechanical valves (74 ± 9% at 15 years) (p > 0.64). Conclusions. Mechanical valves are most suitable for younger patients with native valve endocarditis; however, tissue valves are acceptable for patients greater than 60 years of age with native or prosthetic valve infections and for selected younger patients with prosthetic valve infections because of their limited life expectancy.