Treatment of chronic hepatitis C consists of inteferon plus ribavirin. The major adverse effect of ribavirin is hemolytic anemia, a complication that limits therapy. Folic acid supplementation is used to improve erythropoiesis in chronic hemolytic anemia. The aim of this study was to evaluate the effectiveness of folic acid supplementation in the prevention of ribavirin-induced anemia in patients being treated for hepatitis C. Twenty one patients enrolled in treatment protocols for hepatitis C received folic acid 1 mg daily and 22 did not. Groups were similar in age, gender, ribavirin dose and baseline hemoglobin. Folic acid supplementation had no effect in the decrease in hemoglobin or the measured parameters of hemolysis. No difference between males and females was noted for hemoglobin decrease or lowest hemoglobin levels. In our study, folic acid showed no beneficial effect in the prevention of ribavirin-induced anemia.