BACKGROUND AND AIMS: The prevalence of functional dyspepsia (FD) in the general population is not known. The aim of this study is to measure the prevalence of FD and its risk factors in a multiethnic volunteer sample of the U.S. population. METHODS: One thousand employees at the Houston VA Medical Center were targeted with a symptom questionnaire asking about upper abdominal symptoms, followed by a request to undergo endsocopy. Dyspepsia was defined by the presence of epigastric pain, fullness, nausea, or vomiting, and FD was defined as dyspepsia in the absence of esophageal erosions, gastric ulcers, or duodenal ulcers or erosions. The presence of dyspepsia and FD was examined in multiple logistic regression analyses. RESULTS: A total of 465 employees completed the relevant questions and of those 203 had endoscopic examination. The age-adjusted prevalence rate of dyspepsia was 31.9 per 100 (95% CI: 26.7-37.1), and 15.8 per 100 (95% CI: 9.6-22.0) if participants with concomitant heartburn or acid regurgitation were excluded. Subjects with dyspepsia were more likely to report smoking, using antacids, aspirin or nonsteroidal antiinflammatory drugs (NSAIDs), and consulting a physician for their symptoms (p < 0.05) than participants without dyspepsia. Most (64.5%) participants with dyspepsia who underwent endoscopy had FD. The age-adjusted prevalence rate of FD was 29.2 per 100 (95% CI: 21.9-36.5), and 15.0 per 100 (6.7-23.3) if subjects with GERD were excluded. Apart from a trend towards association with older age in the multiple regression analysis, there were no significant predictors of FD among participants with dyspepsia. CONCLUSIONS: Most subjects with dyspepsia have FD. The prevalence of FD is high but predictors of FD remain poorly defined.