Endocarditis due to micrococci and staphylococci other than Staphylococcus aureus has increased with modern cardiovascular surgery. From 1956 to 1971, Micrococcus species and S epidermidis caused 19 instances of endocarditis at the University of California at Los Angeles, accounting for 12% of all such instances. Cardiac surgery had been performed from several days to six months previously on nine patients. All had received antibiotic prophylaxis during surgery. Most of the causative organisms were resistant to penicillin G. Treatment resulted in four cures, three relapses, and two deaths. In the ten patients who had not had recent cardiac surgery, endocarditis followed urologic procedures in three patients and cardiac catheterization and dental prophylaxis in one patient each. In six patients, the causative organism was sensitive to penicillin G. In contrast to the surgical group, all but one patient were cured of endocarditis.