Inflammation is one of the major causes of resistance to erythropoietin (EPO) treatment. In the present study, the relationship between serum C-reactive protein (s-CRP) and the dose of recombinant human EPO required to maintain hemoglobin levels at approximately 12 g/dL was analyzed in 30 hemodialysis patients. The weekly EPO dose in patients with s-CRP > or = 20 mg/L was, on average, 80% higher than in patients with s-CRP less than 20 mg/L. The EPO doses and s-CRP were both inversely correlated to the levels of serum albumin and serum iron, suggesting that the principal mechanism by which inflammatory cytokines inhibit erythropoiesis is coupled to iron metabolism, ie, functional iron deficiency. Our results demonstrate the usefulness of s-CRP as a predictor of resistance to EPO treatment.