A combination of irinotecan hydrochloride (CPT-11; 160 mg/m2, intravenous infusion, day 1) and cisplatin (5-day continuous intravenous infusion; 20 mg/m2/day) was administrated to advanced non-small cell lung cancer patients. They were given Hangeshashin-to (TJ-14), a Kampo medicine, to prevent the occurrence of irinotecan-induced diarrhea. The authors studied the Kampo medicine's clinical usefulness in a randomised comparative trial. Subjects in the study comprised 41 non-resectable and untreated non-small cell lung cancer patients. A daily dosage of 7.5 g Hange shashin-to was divided into three portions, each of which was given to the subjects orally before each meal. The subjects began taking the medicine three or more days before the start of chemotherapy, and continued taking it more than 21 days after starting chemotherapy. A total of 18 patients received TJ-14, and 23 did not. Compared with the latter, those given the Kampo medicine reported a significant (p = 0.044) improvement in the grade of diarrhea, and had a lower incidence of diarrhea grade 3 and above (p = 0.018). However, no differences were seen among the two groups in terms of the frequency of diarrhea and the duration of the diarrhea. As side effects, two patients developed grade 1 constipation. These findings showed that TJ-14 was effective in preventing and alleviating the incidence of diarrhea induced by CPT-11.