OBJECTIVE In vitro electrophysiologic characterization of the peritoneal mesothelium as a barrier for ion transport during peritoneal dialysis. METHODS Experiments were performed on rat's mesentery and diaphragm. Electrophysiologic parameters of the isolated tissue were assessed in the modified Ussing system. RESULTS We have shown that there are significant differences between electrophysiological parameters of the parietal and visceral peritoneum. The value of the potential difference across the parietal mesothelium lining the abdominal part of the diaphragm (PDmpt) was 0.26 +/- 0.03 mV (mean +/- SEM), with a positive charge recorded from the apical side of the mesothelium. Electrical resistance of the mesothelial monolayer (Rmpt) was Rmpt = 13.6 +/- 1.3 omega.cm2 and 1.4 +/- 0.2 omega.cm2 for the tissue isolated from the diaphragm and mesentery, respectively. Both the mechanical and chemical procedures used for the preparation of the peritoneal membrane model from the diaphragm have been shown to produce similar values of electrophysiological parameters. CONCLUSIONS The electrophysiologic approach presented here may be a useful tool for studies of highly permeable biological membranes such as the peritoneal mesothelium. The mesothelial tissue isolated from the rat diaphragm has been shown to be a suitable model for electrophysiologic studies of the peritoneum as assessed by the values of the PDmpt and Rmpt parameters.