Forty-three strains of coagulase-negative staphylococci were obtained from dialysis effluent during 41 episodes of CAPD peritonitis. Eighty per cent of these were found to be Staphylococcus epidermidis but several other species also occurred. A recurrent infection lasting 15 weeks was caused by Staph. haemolyticus. Multiple antibiotic resistance was found to be common. Of 13 antibiotics tested, only vancomycin was active against all strains although most strains were also sensitive to rifampicin, netilmicin and cefamandole. Vancomycin was chosen for the initial treatment of CAPD peritonitis caused by coagulase-negative staphylococci and eradicated the organism in 29 of 30 episodes.