Deferasirox (DFX) is a useful and convenient oral iron chelator, however, some patients require a dose reduction or cessation of DFX because of adverse events. The aim of this study is to determine a predictive marker of response to DFX therapy, allowing us to adjust the appropriate dosage of DFX for patients in early phase of the therapy. We retrospectively analyzed 39 patients (male/female=24/15, median 60 years old, baseline serum ferritin 3034 μg/L), who had received red blood cell transfusions. Blood serum samples of each patient were examined for TIBC, Fe, and serum ferritin every 2 or 4 weeks. A patient with more than 40% reduction of ferritin was defined as a responder. Twenty-three patients responded to DFX, while 16 did not. There were no statistical differences between the two groups on baseline patients' characteristics. Logistic regression analysis showed elevation of TIBC was associated with responders (R2=0.37, p<0.001). Cumulative incidence of response is significant statistical difference between groups with elevation of TIBC greater than 150 μg/dl or not (gray test, p<0.001). Elevation of TIBC (>150μg/dl) predicts effective reduction of ferritin in treatment with DFX by Fine-Gray proportional analysis (HR 29.6, 95%CI 4.8-183.6, p<0.001). The median interval between the time point of TIBC>150 and response was 5 weeks (range 0-20 weeks). These findings suggested that we could effectively adjust the dosage of DFX with monitoring elevation of TIBC.