We evaluated the efficacy of oral glutamine supplementation in children 2 to 60 months of age with persistent diarrhea by 1:1 randomization to standard treatment alone or together with twice daily glutamine. The failure rate was similar in both arms (relative risk: 1.8 [95% confidence interval: 0.8-3.7], P = 0.12). Glutamine supplementation showed no benefit on the outcome of persistent diarrhea.