The corrosion behavior of Zr-Ti and Zr-Hf alloys with various concentrations in properly deaerated Hanks' solution were investigated by electrochemical techniques. The effects of the thermal treatment with the purpose of homogenization of chemical composition on the pitting potentials of the Zr-Ti alloys were also examined. The results indicated that sufficient addition of Ti to Zr improved its corrosion resistance, especially in terms of the pitting potential and the passive current density. On the other hand, addition of Hf totally lowered the corrosion resistance of the alloy. The thermal treatment improved the pitting corrosion property of Zr-Ti alloys, and Zr alloys with over 5mol% Ti showed much higher pitting potentials than that of pure Zr. The treatment also improved the reproducibility of the measurement and narrowed the data scattering. This phenomenon was discussed with the model of rapidly-cooled metallographic structure.