Eosinophilic esophagitis (EoE) is a rapidly emerging chronic immune-mediated condition affecting children and adults, both genders, and all races. A large variation in the prevalence of EoE exists in the literature. The aim of this study is to establish the prevalence of EoE in a military health-care population in the United States using a comprehensive electronic medical record search. Using the International Classification for Diseases-9 code for EoE (530.13), the total number of EoE patients enrolled in the military health-care system from October 1, 2008 to September 30, 2009 including active-duty military, dependents of military personnel, and retirees were identified. For each case of EoE identified, demographic data (age, gender, and race) and geographic location was obtained. The overall prevalence of EoE was calculated as well as the prevalence within subgroups. The geographic regional locations were reported per the U.S. Census Bureau regions (Northeast, South, Midwest, and West). A total of 987 EoE patients were identified from 10,180,515 military health-care beneficiaries, establishing an overall prevalence of 9.7 per 100,000 (95% confidence interval [CI] 9.1-10.3). Seven hundred twenty-eight out of 7,707,372 adult patients were identified, establishing a prevalence of 9.5 per 100,000 (95% CI 8.8-10.1). Two hundred fifty-nine out of 2,473,143 pediatric patients were identified, establishing a prevalence of 10.5/100,000 (95% CI 9.2-11.8). EoE was more prevalent in males (odds ratio [OR] 2.03 [95% CI 1.78-2.32]) and higher in Caucasian versus African Americans (18.1 vs. 5.2/100,000, OR 3.47 [95% CI 2.40-5.03]). EoE was more prevalent in the Western region of the United States compared with the Northeast, South, and Midwest regions, with a prevalence of 11.9 versuss 5.2, 9.6, and 9.2 per 100,000, respectively. When comparing Northern with Southern states, there was an increased prevalence in the North (10.9 vs. 7.2/100,000, P < 0.05). In this large nationwide study, increase in prevalence of EoE was seen in younger adults, with a higher prevalence in Caucasians. Geographically, the western United States had a significantly higher prevalence with a slightly higher prevalence in the Northern latitude.