A multicentre, comparative, randomized study was performed to compare the efficacy and tolerability of two antibiotic regimens in the treatment of peritonitis in continuous ambulatory peritoneal dialysis (CAPD) patients: teicoplanin plus tobramycin versus cephalothin plus tobramycin. After informed consent had been obtained, 68 patients were randomized prospectively to receive either teicoplanin plus tobramycin or cephalothin plus tobramycin. Patients were followed throughout the study and for up to 4 weeks after the end of treatment, when clinical and microbiological parameters were assessed again. The incidence of clinical failure was 4.6 times higher in the cephalothin plus tobramycin group than in the teicoplanin plus tobramycin group (7/28 versus 2/37; P < 0.05). There was no significant difference in bacterial eradication between the two groups. Local and systemic tolerability were good for both regimens. The study shows that teicoplanin plus tobramycin is more effective than cephalothin plus tobramycin and might become a 'first-line' treatment for peritonitis in CAPD patients.