A case of bacterial endocarditis was caused by Cardiobacterium hominis in a 41-year-old man with mitral and aortic incompetence due to a previous episode of rheumatic fever. The main distinguishing characteristics of C. hominis are described, and the incidence of endocarditis is reviewed. After six weeks of treatment with effective bactericidal chemotherapy a microbiological cure was achieved and the patient successfully underwent mitral valve replacement and aortic valve plication.