Twenty-eight of 143 patients treated for infective endocarditis had replacement of one or more cardiac valves within six months after the diagnosis was made. Twenty-two patients (16%) with bacterial endocarditis had operation, and six died in hospital. All six patients with fungal endocarditis required vale replacement, and one died in hospital. Uncontrolled or progressive heart failure was the indication for operation in all patients with bacterial endocarditis. When severe heart failure was present, 5 of 11 patients with bacterial endocarditis died in hospital, and only 1 of 3 patients with associated bacteremia survived. If blood cultures were sterile, the duration of preoperative antibiotic therapy did not correlate with hospital survival. None of the patients with bacterial endocarditis developed prosthetic infections, but two developed paravalvular leak. Massive emboli or persistent mycotic septicemia were the indications for valve replacement in patients with fungal endocarditis. Viable organisms were cultured from the excised valves in all of these patients in spite of preoperative amphotericin B for 30 to 140 days and negative blood cultures. Excision of the infected valve cured the infection in all patients. Five patients died 6 weeks to 36 months after operation. At the present time 16 patients remain alive 14 to 47 months after operation. Six of nine drug addicts are alive 15 to 27 months postoperatively.