A randomized pilot trial was performed to evaluate the feasibility of administration of glutathione (GSH, 1200 mg, i.v.) as a protector in preventing diarrhea in patients operated on for endometrial cancer and submitted to adjuvant radiotherapy of the pelvis. Diarrhea occurred in 52% of patients in the untreated control group and only in 28% of patients in the GSH-treated group. Our preliminary data indicate that GSH administered before radiotherapy reduced the occurrence of diarrhea from oxidative damage to the intestinal mucosa. A large-scale phase III study is required to obtain definitive conclusions on the protective potential of GSH.