It is becoming clear that modern medical practices leading to the compromise of patients (e.g., by the ntroduction of prostheses or • -atheters and immunosuppressive therapy) have greatly enhanced the risk of infection by resident coagulase-negative Staphylococcus species. Table 1 lists the various species according to species group and pathogenic potential. Although Staphylococcus epidermidis and S. saprophyticus are now well documented as opportunistic pathogens, additional research will be required to assess the pathogenicity of the other species, especially with regard to possible site or tissue specificity, severity of infection, and problems with antibiotic treatment. Coagulase-negative staphylococci Ihave been frequently implicated in infections of prosthetic heart valves (7), vascular and joint prostheses (19, 27), and cerebral spinal fluid dshunts (10), subacute bacterial endocarditis (12), peritonitis in patients receiving continuous peritoneal dialysis (21), and in urinary tract (11), eye (25), ear (6), and ~vound (20) infections. They have ,also been isolated frequently from he blood, urine, and tumors of ancer patients, and from these sources often exhibit altered strut~tural and biochemical features (e.g., las L-forms with cell wall deficiencies Table 1 Coagulase-Negative Staphylococcus Species