The plasma concentration of 25(OH) D - calcidiol - is low in most of stage 5 renal patients. Due to the lack of renal 1alpha-hydroxylase, no supplementation is recommended. However, calcidiol also displays many extraosseous beneficial antiproliferative effects. It may be useful to correct its deficiency in dialysis patients. The efficacy of an oral supplementation for 6 months with ergocalciferol, (Sterogyl), was evaluated in a monocentric cohort of 107 prevalent hemodialysis patients. Plasma levels of 25(OH) D, parathormone, total and ionized calcium, phosphates, were measured at month 0, 3 and 6 in all patients and plasma levels of 1-25(OH) D at month 0 and 6 in 38 patients with the lowest 25(OH) D levels at baseline. Patients were divided into four groups according to their initial 25(OH) D plasma levels and received ergocalciferol supplementation in accordance to the KDOQI Guidelines for stage 3 and 4 renal patients.101/107 patients display low levels of 25(OH) D at baseline: mean 11.8+/-11.6 microg/l (normal> 30 microg/l). At the end of the initial three months correction period, the plasma levels of 25(OH) D rose significantly. However, only 60% of patients reach a normal plasma concentration of calcidiol with the highest - 600,000UI - ergocalciferol cumulative dosage. At the end of the three months maintenance period, plasma 25(OH) D concentrations fell in all patients. No significant change was observed in parathormone, calcium, phosphates and 1-25(OH) D plasma levels. There was no hypercalcemic episode.KDOQI ergocalciferol recommended doses for stages 3 and 4 renal patients did not correct calcidiol deficiency in hemodialysis patients. New prospective studies are required for defining the modalities of an efficient vitamin D supplementation with ergocalciferol or cholecalciferol.