One of the major side effects of ribavirin/interferon alpha combination therapy for chronic hepatitis C is hemolytic anemia. One of the causes of hemolytic anemia is considered to be decreasing deformability of erythrocytes resulting from the accumulation of phosphorylated ribavirin in erythrocytes. The administration of eicosapentaenoic acid (EPA), which has a wide variety of pharmacological actions, increases the deformability of erythrocytes. We conducted an uncontrolled pilot study of EPA therapy for patients with ribavirin-related anemia. Six patients with chronic hepatitis C, who had developed anemia while receiving combination therapy, were treated with an oral ethyl ester of EPA (1800 mg/day) for two months. The hemoglobin level of all six patients increased following EPA therapy. The mean hemoglobin level significantly increased from 10.8 g/dl to 11.4 g/dl one month after therapy was initiated (P<0.05), and this level was obtained again one month later (11.5 g/dl). None of the patients developed an adverse reaction. These findings suggest that EPA has a beneficial effect in patients with ribavirin-related anemia. Further study is required to confirm our results.