This paper presents an interim report on the findings of the International Peritoneal Biopsy Registry (IPBR). The registry was set up for the collection and morphological examination of specimens of peritoneal tissue obtained at surgical implantation or removal of the catheter before, during or after treatment with continuous ambulatory peritoneal dialysis (CAPD). The key objective of the Registry is the accumulation of information on the effect of peritoneal dialysis, peritonitis and any other complication of the therapy, on the structural integrity of peritoneal mesothelium, stroma and blood vessels.