The Epstein-Barr virus (EBV) has been detected in certain types of lymphoma and some epithelial neoplasms including nasopharyngeal lymphoepithelioma, and rare lymphoepithelioma-like carcinomas occurring in a variety of organs including, most recently, the stomach. The authors investigated the possibility that EBV may be present not only in the rare gastric cancers that resemble nasopharyngeal lymphoepithelioma, but also in typical gastric adenocarcinoma. EBV sequences were detected in 22 of 138 (16%) cases of typical gastric adenocarcinoma by polymerase chain reaction and in situ hybridization (ISH) techniques. The EBV genomes were specifically present within the gastric carcinoma cells in an even distribution. The EBV genomes were also present in adjacent dysplastic epithelium but were absent in surrounding lymphocytes, other normal stromal cells, intestinal metaplasia, and normal gastric mucosa. The EBV genomes in the infected gastric carcinoma cells are expressed as EBV RNA was detected by ISH. EBV was most often detected in gastric tumors from men (21%) compared with women (3%). Thus some cases of gastric adenocarcinoma are EBV-associated.