This study compared the static and kinetic activities, in both broth and used-dialysate, of selected antibiotics against 23 strains of coagulase-negative staphylococci causing peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD). Vancomycin was shown to be effective against all isolates with similar rates of kill to flucloxacillin and cefuroxime, although a few strains were found to be resistant to cefuroxime. Gentamicin was rapidly bactericidal for sensitive strains which accounted for 60% of the strains tested. Fusidic acid was associated with significant resistance and lack of bactericidal activity in the kinetic studies. Emergence of resistance occurred with rifampicin. The combinations clavulanic acid/amoxycillin and sulbactam/ampicillin generally showed good static activity. In addition a broad range of biotypes and phage types were demonstrated among these organisms with biotype SII (Staphylococcus epidermidis) predominating. There was no correlation between biotype and antibiogram.