The purpose of this study was to evaluate the sTfR-F index and hypochromic erythrocytes (HYPO%) as potential predictors of response to recombinant human erythropoietin (r-HuEPO) of anemic patients with multiple myeloma (MM) before treatment, as well as early in the course of treatment. Twenty-six newly diagnosed anemic MM patients received r-HuEPO 30,000 IU/wk sc, for six weeks. The sTfR-F index and HYPO% were determined at baseline and at weeks 2 and 6. Patients were classified in 1 of 4 categories of a diagnostic plot, according to erythropoietic state (ES I-IV), defined by the combination of sTfR-F index and HYPO%. Sixteen of 20 patients in ES I and II before treatment responded to r-HuEPO, whereas none of the 6 patients in ES III and IV responded (P < .001). At week 2, 44% of patients who responded and 60% of the nonresponders were in functional iron deficiency (FID) and the proportion increased to 69% and 80%, respectively, by week 6. Seven of the patients who did not respond received in addition 200 mg iron sucrose IV weekly, for the next 4 weeks, and 6 of them responded. These results suggest that combination of sTfR-F index and HYPO% in a diagnostic plot can be used as a predictive model to recognize patients who will benefit from r-HuEPO and identify FID requiring iron supplementation, before treatment and early in the course of treatment, contributing thus to optimization of r-HuEPO therapy.