['Emerging evidence suggests that the mass distribution of azithromycin for trachoma control (MDA) may increase circulation of macrolide resistance in bacteria associated with severe pediatric infections in treated communities.', 'We examined the effect of MDA on nasopharyngeal carriage of antibiotic-resistant Streptococcus pneumoniae among 1015 young children living in rural Tanzania. MDA with a single dose of oral azithromycin was provided in 4 of 8 communities where trachoma prevalence was ≥10%. Isolates were tested for susceptibility to azithromycin (AZM) and commonly used antibiotics by disk diffusion and Etest. We calculated the proportion of antibiotic-resistant S. pneumoniae carriage at baseline and again 1, 3, and 6 months after treatment, and at comparable intervals in the untreated villages.', 'The proportion of AZM-resistant isolates was similar between groups at baseline (MDA: 35.8% vs non-MDA: 35.4%), however, this proportion was greater in the MDA group in all subsequent surveys. At 6 months, the percentage of AZM-resistant isolates was significantly higher in the MDA group (81.9% vs 46.9%, P < .001). The odds of AZM-resistant carriage was 5-fold greater in the MDA group (odds ratio, 4.95 [95% confidence interval, 3.23-7.61]). The proportion of isolates clinically resistant to AZM (minimum inhibitory concentration ≥16 µg/mL) was also significantly greater in the MDA group at 6 months (35.3% vs 12.4%, P < .006).'] Is mass distribution of azithromycin for trachoma control associated with increased risk of azithromycin-resistant Streptococcus pneumoniae carriage in young children 6 months after treatment?