The purpose of this study was to determine the influence of oral glutamine supplement on exercise performance in endurance swimmers. Ten male swimmers, 13 to 18 years of age, all specialized in 400-m and/or 800-m distances, participated in this investigation. The athletes were divided in two groups, placebo group with five swimmers, that ingested 5/day of corn starch, and glutamine group with five swimmers that ingested 5/day of glutamine. The swimmers received the intervention for 30 days. The exercise performance measures (800-m time trial and anaerobic threshold, crawl technique) were obtained before and after the intervention. To compare results paired t test was used. There weren’t significant differences in the results of 800-m time trial and anaerobic threshold, in both groups. These data suggest that this oral glutamine supplementation dose didn’t influence exercise performance in endurance swimmers. Keywords: Swimming. Glutamine. Performance.