【Abstract】Objective To longitudinal observe the CA125 l evels and peritoneal transport function of peritoneal dialysis patients. Methods Peritoneal dialysis effluents CA125 levels (d-CA125) were measured by micro-particle enzymic immune assay, peritoneal transport function was judged by 4hours dialysate creatinine/serum creatinine ratio (4h D/P Cr). Results d-CA125 concentration and appearance rate in 4hours dwell-time were signficant lower than that of 2 years ago; There was significant increase in 4h D/PCr after 2 years; d-CA125 concentration who suffered from infective peritonitis were significantly increased and d-CA125 levels reduced to the usual levels after peritonitis recovery; CA125 levels had no correleted with 4h D/PCr both 2 years ago and after 2 years. Conclusion d-CA125 levels decreased with peritoneal dialysis duration while peritoneal transport function increased by longitudinal observation.. Injuries of peritoneal mesothelial cells might not be result from the increase of peritoneal transport function.