Abstract: Objective To investigate the protective and therapeutic effects of glutamine on radiationinduced diarrhea in pelvic radiotherapy. Methods Sixty-three patients suffered from cervical carcinoma or endometrial cancer were randomly divided into glutaminetreated group and control group. The glutamine（100ml, once a day, total 10 times） was administered intravenously every day in the last two weeks of the radiation period only in the glutaminetreated group. The incidence and severity of acute diarrhea were analyzed between groups as well as the frequency and dosage of antidiarrheal medication. Results The overall diarrhea incidence of glutamine-treated group and control group were 87.1％ and 90.6％，respectively. There was no significant difference between two groups（P＞0.05）. The average times of diarrhea everyday in both groups were 2.6 and 3.0 times with no significant difference（P＞0.05）. In the fifth week， the average times of diarrhea everyday in glutaminetreated group were less than those in the control group（P＜0.05）. The frequency and dose of antidiarrheic in the glutaminetreated group were less than those in the control group（P＜0.05）. Conclusion Glutamine is an effective therapy on radiationinduced diarrhea， but the protective effects needs more clinical trial.