Gastric adenomas are neoplastic growths characterized by localized, polypoid proliferations of dysplastic epithelium. They frequently arise in stomachs with a background of mucosal atrophy and intestinal metaplasia, and a higher risk of adenocarcinoma elsewhere in the stomach has been reported in patients with gastric adenomas. Additionally, some gastric adenomas themselves demonstrate neoplastic progression to infiltrating adenocarcinoma. However, previous studies have not comprehensively evaluated the background gastric mucosa and risk of adenocarcinoma, particularly in relation to the histologic classification of adenomas as either intestinal-type or gastric-type. We studied 61 gastric adenomas from 51 patients between 1985 and 2001. The adenomas were classified as intestinal-type (containing at least focal goblet cells and/or Paneth cells), gastric-type (lined entirely by gastric mucin cells on PAS/alcian blue stain), or indeterminate. We evaluated the histologic features of both the adenomas (location, multiplicity, degree of dysplasia, presence of adenocarcinoma within the polyp) and the surrounding gastric mucosa (presence of gastritis, intestinal metaplasia, and adenocarcinoma). Gastric adenomas were distributed equally throughout the stomach, were most frequently solitary (82%), and contained adenocarcinoma in nine cases (14.8%). There were 34 intestinal-type adenomas (56%) in 31 patients, 25 gastric-type adenomas (41%) in 18 patients (including 10 patients with familial adenomatous polyposis), and 2 of indeterminate type (3%). Intestinal-type adenomas were significantly more likely than gastric-type adenomas to show high-grade dysplasia (p <0.0001), adenocarcinoma within the polyp (p = 0.016), intestinal metaplasia in the surrounding stomach (p <0.000001), and gastritis (p = 0.002). Patients with intestinal-type adenomas were also more likely to have separate adenocarcinomas (five cases vs 0 cases), although this did not reach statistical significance. Gastric adenomas are rarely truly "sporadic" lesions. In any individual patient complete removal of the adenoma should be performed, and thorough biopsy of the surrounding gastric mucosa is essential to understand the clinicopathologic context of the adenoma.