|Abstract||Prior research suggests probiotic consumption provides many health benefits to the consumer. Evidence from recent studies indicates that probiotics may alter mood via the gut-brain axis. The alterations in mood shown in previous research are attributed to alterations in GABAA receptor subunit expression. GABA is the primary inhibitory neurotransmitter, and manipulation of ion flow through GABA receptors is a reliable way to manipulate anxiety. The goal of the current study was to investigate how daily administration of probiotics affected the expression of anxiety behaviors in the treated animals. We hypothesized that daily administration of Lactobacillus reuteri would result in decreased expression of anxiety behaviors. Newly weaned animals were fed daily either a 10% sucrose sterile broth solution, or a 10% sucrose broth solution containing L. reuteri (10^9 colony forming units per dose), until all animals were 70 days of age. Following the administration period, animals were tested over three days on measures of anxiety. On day 1, animals were tested on the elevated zero maze. On day 2 and 3, animals were tested in an open field apparatus. Following the behavioral tests, a corticosterone ELISA was performed. The results from our behavior tests support the hypothesis that chronic treatment with L. reuteri can reduce behavioral measures of anxiety behaviors. At this time, there were no statistically significant differences observed in the results from the corticosterone ELISA. With these results, the use of probiotics in relation with anxiety reduction seems promising.