While vitamin D supplementation is safe and effective in repleting vitamin D levels in dialysis patients, the impact on anemia is unknown. The majority of hemodialysis patients require erythropoietin supplementation to maintain their serum hemoglobin between 11 and 12 gm/dL, a drug that is both costly and associated with significant side effects. If repletion of vitamin D significantly decreases erythropoietin requirements in hemodialysis patients, it would result in a substantial reduction in patient care costs. Our aim is to study the impact of ergocalciferol supplementation in hemodialysis patients with 25-hydroxyvitamin D deficiency. The investigators anticipate approximately 30% reduction in erythropoietin dose requirement in our hemodialysis population.