Vitamin D may be associated with bone marrow function. Our previous investigation found an association of vitamin D25 (D25) deficiency and anemia in subjects with and without CKD. We investigated whether correction of D25 deficiency in patients with CKD may improve anemia and decrease need for erythrocyte stimulating agents. A retrospective cohort study of patients with CKD who were treated for anemia between 1/1/2006 to 7/31/2007. Inclusion criteria were: two or more serum D25 level data at least three months apart from the first and the second set, and known hemoglobin levels and EPO dosages within 1 month of the D25 levels. D25 repletion varied in terms of dose and schedule. The primary end point of the study was the percent change in the EPO dose needed to maintain target hemoglobin (11-12 g/dl). Exclusion criteria were active GI bleed, active infections, ferritin level >1000, vitamin B12 or folate deficiency, and a diagnosis of cancer. Total of 160 patients met the inclusion criteria out of 250. Statistical analysis of inverse correlation of change in D25 levels with change in EPO doses showed no significant relationship. Our study is limited by a small sample size, the retrospective nature of our study design, and lack of a control group. This study underscores the need for a prospective intervention trial of the effects of D25 repletion on anemia.