Background. Epstein-Barr virus (EBV), the etiological agent of infectious mononucleosis, has an important role in the oncogenesis of EBV-related malignant diseases. The association of EBV with gastric carcinoma cells has become well known recently, but there are only a few reports concerning its association with surrounding epithelia and infiltrating lymphocytes. In this study, we investigated the association of EBV with gastric carcinoma and surrounding cells. Methods. One hundred and two cases of gastric carcinoma were studied. The specimens were studied for the presence of the EBV genome by polymerase chain reaction (PCR), and then by in situ hybridization (ISH) technique to determine the localization of EBV. Results. Of 97 informative cases, EBV was detected in 21 cases (21.6%) by the PCR method. ISH studies showed that EBV RNA was expressed in 5 of the 97 cases (5.2%) and was localized to the nuclei of carcinoma cells. All these 5 lesions were found in male patients. In these 5 cases, 3 were diffuse type and 2 were intestinal type, and all cases arose in the proximal region of the stomach. EBV RNA was not detected in non-neoplastic epithelia, but it was detected in 24 of the 97 cases (24.7%) in small lymphocytes. Conclusion. EBV was detected in 5.2% of gastric carcinomas and in 24.7% of infiltrating lymphocytes by the ISH method. The high positive rate (21.6%) by the PCR method corresponds to the presence of the EBV genome in surrounding lymphocytes.