Primary gastric lymphoma is the most common form of extralymphatic non-Hodgkin's lymphoma (NHL). Most cases are of B-cell origin and few cases of lymphoma of T-cell origin have been reported. Peripheral T cell lymphoma is a lymphoma of extrathymic origin. Expression of T-cell intracellular antigen (TIA)-1 can be detected in all cytotoxic cells, and the expression of this cytotoxic protein is associated with extranodal presentation. We report a case of primary peripheral T cell lymphoma of the stomach with cytotoxic T-cell phenotype in a 70-year-old male presenting with upper gastrointestinal bleeding. (Korean J Gastrointest Endosc 2004;28:7680)