To assess the effects of Byakko-ka-ninjin-to on thirst and body weight gain in chronic hemodialysis patients with excessive interdialytic body weight gain, 8 patients (4 men and 4 women, ranging in age from 47 to 75) were prescribed Byakko-ka-ninjin-to extract tablets, 6-12 tablets per day, for 10 weeks. In 4 of the patients, thirst symptoms improved, resulting in significant reduction of interdialytic weight gain. This effect continued to be significant even after cessation of the agent. In the cases of 4 patients whose thirst symptoms did not improve, interdialytic weight gain was not reduced either during or after treatment. For all 8 patients, there were no significant changes in cardiothoracic index, and no adverse effects or events were observed either during or after treatment. Significant reduction in interdialytic weight gain was observed only in the patients with reduced thirst, which suggests that Byakko-ka-ninjin-to allows patients to limit their weight gain by drinking less. These results suggest that Byakko-ka-ninjin-to could be a useful and safe agent to reduce excessive interdialytic body weight gain, at least in a significant cohort of chronic hemodialysis patients.