Aspirin is widely used for its antiplatelet activity, but it harbors a risk of severe adverse gastrointestinal effects, such as bleeding and perforation, especially in elderly people. Our aim to assess the prevalence of upper gastrointestinal lesions and the effect of aspirin on the gastrointestinal mucosa in asymptomatic subjects taking minidose aspirin (100 to 325 mg per day) for more than 3 months. A prospective, open design was used. Patients attending the ophthalmology and cardiology outpatient clinics who had a medical history of more than 3 months of regular aspirin consumption were referred for esophagogastroduodenoscopy (EGD). Of the 90 patients referred for EGD, 44 were symptomatic (epigastric pain or dyspepsia) and were excluded from the study. The 46 asymptomatic patients included 22 men and 24 women of mean age 70 +/- 10 years (range, 36 to 87 years); 32% were current or former smokers. Mean daily aspirin dose was 129.34 +/- 76.61 mg. Only 24% were taking a gastroprotective agent. EGD revealed ulcer or erosions in 47.83% of the patients: erosive gastroduodenitis in 13 patients, gastric ulcer in 14, duodenal ulcer in 2, and gastric and duodenal ulcers in 2. Urease test for Helicobacter pylori infection was positive in 26%. Univariate and multivariate analysis revealed no factor other than aspirin predictive of a positive endoscopy. Minidose aspirin treatment is associated with a high prevalence of ulcerations of the stomach and duodenum.