Skin biopsies were taken from 63 patients with end-stage renal failure (ESRF) and 5 normal volunteers, 53 of whom were on maintenance hemodialysis (HD) and the other 10 without HD. They were examined with light and electron microscopy and subepidermal capillaries were subjected to image analysis. Thickening of the basement membrane (BM) with multilamination of the basal lamina, endothelial activation and chronic inflammatory cell infiltration with participation of mast cells were evident. The extent of these BM changes was correlated with the duration of HD, but not significantly correlated with the clinical findings indicative of arteriosclerosis. There was significant correlation between the duration of HD and mast cell proliferation or eosinophilia. We suspect that the subepidermal capillary changes represent an inflammatory reaction provoked by uremic toxins or by the repeated use of an artificial organ.