Increasing the survival of patients on CAPD is related to the long-term reliability of the peritoneal access. Six silicone Tenckhoff catheters (with strip or diffuse barium sulphate inclusion) removed after 39-69 months because of the appearance of external segment fissures, were analysed by scanning electron microscopy (SEM) and infra-red spectroscopy with attenuated total refractance (ATR). The extracorporeal portion of the catheters showed (by ATR) a more prominent oxidation peak on the external than the internal surface; SEM showed marks and cracks on the external surface and exfoliation and flattening of the silastic reticle on the intraluminal surface. No evidence of oxidation was found in the intra-abdominal portion of the catheters but biofilm was found. We suggest that barium sulphate may render the silastic brittle and physiological and environmental long-term factors (such as uv-rays, temperature, sweat and disinfectants) could cause oxidation and loss of physico-chemical properties, with critical aging of the silastic and loss of catheter resistance to mechanical injury.