Background and Aims: Gastroesophageal reflux disease (GERD) reportedly has increased in prevalence while Helicobacter pylori infection and peptic ulcer disease have been on the decrease. The aim of the present study was to examine the prevalence of GERD as well as the clinical, endoscopic and histologic variables that associate with GERD in patients referred for endoscopy. Patients and Methods: The study population was drawn from 1,562 consecutive patients referred for endoscopy. The exclusion criteria were previous H. pylori eradication, gastric surgery, anemia and weight loss. Thus 1,128 patients were enrolled in the present study. Results: Of the 1,128 patients, 199 (18%) were referred for endoscopy due to heartburn and/or regurgitation. GERD, defined as chronic (>6 months) heartburn and/or regurgitation with or without erosive esophagitis, Barrett’s esophagus, esophageal ulcer or stricture, was detected in 248 (22%) patients. Of the 248 GERD patients, 81 (33%) had endoscopy-negative GERD, but of those aged <50 years (n = 67), 57 (85%) were endoscopy-negative. The overall incidence of GERD was 307 per 100,000 population/year and that of endoscopy-positive GERD 207/100,000/year. The positive and negative predictive values of heartburn and regurgitation for endoscopy-positive GERD were 0.37 (95% CI 0.31–0.44) and 0.90 (95% CI 0.88–0.92), respectively. Independent risk factors for GERD were male sex (OR 1.9, 95% CI 1.3–2.7), previous medication for upper gastrointestinal symptoms (OR 2.7, 95% CI 1.7–4.1), the use of nonsteroidal anti-inflammatory drugs (NSAIDs; OR 2.0, 95% CI 1.3–3.0), histologic esophagitis (OR 2.2, 95% CI 1.5–3.2) and incomplete intestinal metaplasia at the gastroesophageal junction (OR 1.7, 95% CI 1.0–3.1). Chronic gastritis was protective against GERD (OR 0.7, 95% CI 0.5–0.9). No association was observed between GERD and H. pylori infection. The risk of patients aged <50 years (n = 407) of having major lesion (Barrett’s esophagus, esophageal stricture, peptic ulcer, esophageal/gastric carcinoma) was significantly lower than that of patients aged >50 years (n = 721; OR 0.5, 95% CI 0.3–0.9, p = 0.01). Conclusions: The correlation between reflux symptoms and endoscopy-positive GERD is poor and most GERD patients aged <50 years have endoscopy-negative GERD. The use of NSAIDs is a risk factor for GERD, whereas chronic gastritis, but not H. pylori infection, may protect against GERD. Incomplete intestinal metaplasia at the gastroesophageal junction is associated with GERD.