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We analyzed 52 surgically excised ePTFE grafts used as secondary vascular access in chronic hemodialysis patients, structurally and histopathologically. Pseudoaneurysm formation at the site of repeated venipuncture was the main cause of surgical removal later than two years after implantation. Repeated needle punctures, twice per treatment, two or three times a week may result in a perigraft fibrous tissue capsule directly above areas where the graft was punctured. The delicate microporous structure of the graft wall was shown to be disrupted by needle punctures. The needle puncture sites were filled by surrounding connective tissue, and in one case, capillary formation was observed within the puncture sites. Examination by both light and scanning electron microscopy demonstrated identical patterns of pseudointima on the luminal surface. A thin pannus of endothelium-like cells, confined to the vicinity of the anastomoses, was noted in only four cases. On other areas of the luminal surface without endothelium, a red coagulum incorporating blood cells and fibrin was observed. Histological evidence of acute infection was absent in 61% of the cases and only 27% were considered to be clinically infected. Careful needle puncture technique, systematic rotation of puncture sites, and the use of rigorous aseptic technique are essential in preserving the long-term structural integrity of the vascular access, despite the good mechanical properties and reasonable good resistance to infection of ePTFE grafts.