In recent, telomerase has been drawing the attention, because it plays important role in cell immortalization. Since Kim et al exploited TRAP (telomeric repeat amplification protocol) assay which detected telomerase activity efficiently, telomerase activity of various tissues have been detected. In this study, telomerase activity of gastric cancer of resected or biopsy specimen were detected. And we have examined relationship between telomerase activity and clinicopathological factors. In advanced cancer, telomerase activity is negative in 2 cases and positive in 17 cases. In case with lymph node metastasis, negative in 3 cases and positive in 14 cases. In differentiated type, negative 1 cases and positive 20 cases. In noncancerous gastric mucosa, telomerase activity is positive in only 2 cases of 9 cases with intestinal metaplasia. Previous results were same in biopsy specimen. In summary, telomerase activity was detected in 76.7% of gastric cancer and most of advanced cancer or differentiated type. Some intestinal metaplasia cases with telomerase activity suggested precancerous stage.