Skin biopsies of 33 uremic patients-13 patients on continuous ambulatory peritoneal dialysis (CAPD), 12 on hemodialysis (HD), 8 patients with end-stage renal disease (ESRD) before initiation of dialysis treatment-and 10 healthy volunteers were investigated to determine the number of Langerhans cells (LC) by light microscopy after staining for S-100 protein. The epidermal LC count was significantly lower in patients on CAPD (mean: 62.9 LC/mm2; p = 0.027) and patients on HD (mean: 30.4 LC/mm2; p = 0.0015) compared to controls (mean: 110.1 LC/mm2) and uremic patients before initiation of dialysis treatment (mean: 122.6 LC/mm2). The difference between LC counts of CAPD and HD patients did not reach statistical significance (p = 0.057). There was no relation between LC count and age (p = 0.057) or epidermal width (p = 0.26). No statistically significant correlation could be demonstrated between duration of dialysis and LC count (r = -0.33, p = 0.10). LC counts of CAPD patients with diabetes mellitus (n = 7) were not significantly different from those of nondiabetics (n = 6; p = 0.77). LC counts seem to be normal in uremic patients before dialysis treatment. The reduction in LC density in the skin of dialysis patients may contribute to immunodeficiency of uremic patients on regular dialysis treatment.