has emerged as a potential important cause of childhood morbidity in sub-Saharan Africa. Biannual mass azithromycin distribution has previously been shown to reduce all-cause child mortality in sub-Saharan Africa. We conducted a randomized controlled trial in Burkina Faso in which children were randomized in a 1:1 fashion to a 5-day course of azithromycin or placebo to investigate the effect of oral antibiotics on the gut microbiome. We evaluated the changes in the gut microbiome of preschool children treated with azithromycin using metagenomic DNA sequencing. We found that three species were reduced with azithromycin treatment compared with placebo. These results were consistent with other studies that have shown decreases in species after azithromycin treatment, generating the hypothesis that a decrease in may contribute to observations of reduction in mortality following azithromycin distribution.