Serum levels of tumor necrosis factor-α (TNF-α) and of erythropoietin (Epo) have been evaluated in 100 patients with B-cell chronic lymphocytic leukemia (CLL) in order to determine whether these factors could be significant in the development of anemia, which was observed in some cases with advanced disease. In our series of patients, TNF-α serum levels had an inverse correlation with hemoglobin levels (r = –0.813). In patients with anemia, the serum levels of TNF-α were significantly higher (p = 0.022) than in those without anemia (186.7 ± 84.7 vs. 39.8 ± 20.7 pg/ml). Serum Epo levels were also significantly (p = 0.0003) increased in CLL patients with anemia compared to those without (134.1 ± 225.9 vs. 12.3 ± 4.8 mU/ml). The ratio of observed/predicted (O/P) serum Epo was adequate (>0.8) for the degree of anemia in 70% of patients with anemia and inadequate in the remaining 30%. In the latter, the mean serum TNF-α level was significantly higher (p = 0.005) than the mean for the anemic cases with an adequate O/P ratio of serum Epo (234.1 vs. 166.4 pg/ml). These data suggest that although CLL anemia is not characterized by inadequate Epo production, in some CLL patients this factor may be correlated. In these cases, the levels of TNF-α were significantly higher than in other anemic cases. Compared to other CLL patients with anemia, these CLL patients might better respond to therapy with recombinant human Epo in pharmacological doses.