AIM: To examine the 2′,5′-oligoadenylate synthetase activity and the peritoneal pathological changes when using commercially dialysates in order to reveal effects of the peritoneal dialysate biocompatibility on the immune function and morphological changes. METHODS: (1) CAPD animal models were made using dialysates. (2) Dynamic measurements of 2′,5′-oligoadenylate synthetase activity were made by paper chromatography. (3)The pathological changes of the peritoneal mesothelial cells were examined by light microscope. RESULTS: 2′,5′-oligoadenylate synthetase activities in both experimental (dialysis solution groups) and control group were increased and the mesothelial cell began to exfoliate and become thicker with the infiltration of inflammatory cells at different degrees in the experimental groups, while in the Baxter group, no active inflammation was observed. When the peritoneal dialysis stopped, activity of 2′,5′-oligoadenylate synthetase began to be normal in control group and continued to decline in experimental groups.CONCLUSION: Prolonged immune suppression existed with long-term peritoneal dialysis, causing pathological changes of the peritoneum at certain degrees. Different dialysis solutions resulted in different degrees of immuno-supression and peritoneal damages, which was relevant to the biological compatibility of the peritoneal dialysate.