there is considerable evidence suggesting that frequent, intense, long duration exercise is associated with adverse effects on the immune system as shown by a decrease in immune cell numbers and function. this may ultimately be responsible for the increased rate of infection, in particular, upper respiratory tract infection, seen in athletes. it has been suggested that one possible mechanism for this immunosuppression is a decrease in plasma glutamine. glutamine is a non-essential amino acid that is utilized at a high rate by immune cells. a decrease in plasma glutamine may then impair immune function and possibly lead to increased rates o f infection. recent research has shown that plasma glutamine levels are decreased during times of metabolic and catabolic stress, such as cancer, burns, surgery, endurance exercise and overtiaiiung. this decrease in plasma glutamine coupled with the immunocompronused state of these individuals may be evidence of the important role of glutamine in immune function recent research has shown that glutamine supplementation results in increased immune cell counts and immune function, and decreased rates of infection in various populations. therefore, the purpose of this study was to determine the effect of oral glutamine supplementation on resting blood and saliva immune parameters in endurance trained athletes. fifteen endurance athletes (male= 9, female = 6, age = 27.9 ± 2.2 yrs, height = 177.0 ±2.1 cm, weight=68.5 ± 2.8 kg, running = 64.1 ± 3.2 km/wk) participated in a randomized double-blind glutamine/placebo cross-over study. thirty grams of glutamine or placebo was provided for a duration of 2 weeks, separated by a 4 week washout resting blood and saliva was collected before and after each supplementation period and was analyzed for, total leukocytes, neutrophils, monocytes, lymphocytes, t cells, b cells, natural killer, cd4, cd8 cells, saliva iga and plasma glutamine using a 2-way repeated measures factorial anova. the effect of gender was analyzed by a 3-way mixed plot factorial anova. as well, subjects completed a nutritional analysis, a life stress questionnaire and a training log during the supplementation periods in order to monitor any changes in these control variables. statistical analysis revealed that leukocyte and neutrophil count as well as percent neutrophils for female subjects significantly increased by 13.7 %, 33.5 %, and 16.1 %, respectively following glutamine supplementation, while those receiving placebo decreased by 132 %, 23.2 %, and 10.5 %, respectively (p<0.05). there was no significant change (p>0.05) in any immune parameters of male athletes. this data suggests that under these conditions oral glutamine supplementation may be an effective method of increasing leukocyte and neutrophil counts in endurance trained females.