Peritonitis is one of the most frequent complications of continuous ambulatory peritoneal dialysis (CAPD). Necrosis and exfoliation of the mesothelial cell layer of the peritoneum develop during the acute phase of peritonitis. Agents that hamper regeneration of mesothelial cells will cause delayed recovery of the peritoneal surface, which results in continuous exposure of underlying stem cells to the stimulation of growth factors and possibly leads to peritoneal fibrosis syndrome. The aim of the present study is to determine the effects of several intraperitoneal antibiotics on human peritoneal mesothelial cell (HPMC) growth at their usual loading and maintenance doses. HPMCs were isolated from human omenta. Proliferation of HPMC was evaluated by modified methyltetrazolium assay and cell membrane integrity was assessed by lactate dehydrogenase method. The results showed that most cephalosporins exert an inhibitory, even toxic, effect on HPMCs at their loading doses. Cephalothin, cephradine, cefamandole, cefoxitin, cefuroxime and cefoperazone inhibited HPMC proliferation at their maintenance doses. Vancomycin, clindamycin, aztreonam, piperacillin, imipenem, tobramycin and ceftriaxone have no effect in their usual intraperitoneal doses. From the viewpoint of peritoneal protection, not only drug sensitivity of the causative microorganisms but also effects of antibiotics on HPMC regeneration should be considered when selecting antibiotics for CAPD peritonitis.