Seventy-five episodes of continuous ambulatory peritoneal dialysis (CAPD) peritonitis were studied during a 1 year period at the Queen Elizabeth Hospital, Birmingham. When two simple culture methods were used in parallel, the causative organisms were identified in 97% of cases. Nearly two thirds of episodes of peritonitis were caused by coagulase-negative staphylococci (C-NS), many of which were multiply antibiotic-resistant. On the basis of detailed antibiotic sensitivities, intraperitoneal vancomycin and tobramycin were chosen for the initial treatment of CAPD peritonitis. With this regime, a cure was achieved in 32 of 38 episodes, compared with 15 of 27 episodes when cefuroxime was used. All but 1 of 24 episodes caused by C-NS were cured by vancomycin.