Seventeen of 1,494 patients (1.1%) succumbed to infection following open-heart operations at New York University Hospital between January, 1968 and December, 1971. All but two of these patients had Starr-Edwards ball-valve prostheses inserted. One had repair of a tetralogy of Fallot, and one had aortic commissurotomy and a double coronary bypass graft. The sites of infection were pulmonary (15 patients), urinary tract (14), mediastinum or pleura (10), and blood (15). Pulmonary infection appeared as the source of endocarditis in 13 patients and as a source of pleural or mediastinal infection in nine. Candida species infection was directly responsible for the deaths of 10 of the 17 patients, being the sole organism isolated in 5 of the 10. Predisposing factors to infection were preoperative bacterial endocarditis 2 patients, prolonged cardiopulmonary bypass (>3½ hours) 6 patients, a "low output" state following operation 12 patients, postoperative cerebral dysfunction 6 patients, and postoperative disseminated intravascular coagulation 4 patients. The debilitated state of the patients, multiple sites of infection, degree of tissue destruction, and the variety and resistance of the organisms involved all combined to produce treatment failure. Removal of the infected valvular prosthesis coupled with antimicrobial therapy is considered the treatment of choice in instances of bacterial endocarditis when chemotherapy fails and in all cases of established fungal endocarditis.