OBJECTIVE : Prior studies have shown that about 90% of all carcinoid tumors occur in the GI tract. However, epidemiological studies of these tumors have been limited by small sample size. Our aim was to obtain a more robust epidemiologic survey of large bowel carcinoids (LBC), using population-based data in order to more accurately identify risk factors for these tumors. METHODS : We used a commercial database (Explorys Inc, Cleveland, OH) which includes electronic health record data from 26 major integrated US healthcare systems. We identified all patients aged 18 and older who were diagnosed with LBC, excluding appendiceal carcinoids, between 1999 and 2018 based on Systematized Nomenclature Of Medicine-Clinical Terms (SNOMED-CT) and evaluated the prevalence of LBC. We also performed univariate analysis to describe age-, race-, and gender-based distributions and to identify potential risk factors. RESULTS : Of the 62,817,650 individuals in the database, 4530 were identified to have LBC with an overall prevalence of 7.21/100,000. Individuals with LBC were more likely to be elderly (age > 65) [OR 2.17, CI 2.05-2.31, p < 0.0001], smokers [OR 3.25; 95% CI 3.00-3.53, p < 0.0001], have a history of alcohol use [OR 3.75; 95% CI 3.52-3.99, p < 0.0001], diabetes mellitus (DM) [OR 4.42; 95% CI 4.14-4.72, p < 0.0001], obesity [OR 1.58; 95% CI 1.43-1.74, p < 0.0001], family history of cancer [OR 8.06; 95% CI 7.47-8.71, p < 0.0001], and personal history of ulcerative colitis [OR 6.93; 95% CI 5.55-8.64, p < 0.0001] or Crohn's disease [OR 6.45; 95% CI 5.24-7.95, p < 0.0001]. The prevalence of LBC was less among Caucasians compared to African-Americans [OR 0.57; 95% CI 0.53-0.61, p < 0.0001]. There was no statistically significant gender-based difference; men versus women [OR 1.02; 95% CI 0.96-1.08, p = 0.47]. The most common presenting symptoms included flushing, diarrhea, nausea, weight loss, and abdominal pain, while the most common GI associations included perforation, obstruction, hemorrhage, intussusception, and volvulus. CONCLUSIONS : This is the largest epidemiological study evaluating the prevalence of LBC. We estimated the prevalence rate of LBC to be 7.21/100,000. The presence of significant risk factors with the clinical picture suspicious for a LBC should warrant thorough evaluation as these tumors can lead to life-threatening complications. Further studies are needed to better understand the mechanism of association between these risk factors and LBC.