Fifteen strains of Staphylococcus epidermidis were isolated from the blood of patients of septicemia. They produced white colonies, except two strains, and were negative for both coagulase and egg-yolk tests, indicating that they were of S. epidermidis in its literal meaning. Some of them were positive for both hemolysin and DNase (deoxyribonuclease) formation. When inoculated into mice by the subcutaneous or intraperitoneal route, all of them produced subcutaneous or intraperitoneal abscesses, except 4 strains. When inoculated by the intravenous route, 5 strains caused hemorrhagic or suppurative lesions in the kidneys, but none of the others induced lethal infection, except coagulase-positive strains used as controls.