We described the localization of human telomerase RNA (hTR) expression in human gastric precancerous and cancerous lesions by using in situ mRNA hybridization. Diffusely high hTR expression was found in all carcinoma and adenoma tissues. Partially high hTR expression was seen in 75% hyperplastic polyps, 47% complete-type intestinal metaplasia and 21% incomplete-type intestinal metaplasia. All chronic gastritis without intestinal metaplasia possessed normal levels of hTR expression. The expression of hTR was heterogeneous and infiltrating lymphoid cells also expressed high levels of hTR expression. Taken together, overexpression of hTR due to stem cell hyperplasia is an early event of carcinogenesis of the stomach.