The clinical and radiological aspects are reviewed on the 23 cases of primary malignant lymphoma of the G.I.tract who had been operated on and confirmed histopathologically in Severance Hospital, yonsei University for the duration of 9 years from May 1962 through Aug. 1971. In this series, the small intestine (all in ileum) was the most frequent site of involvement (10 cases; 43.5%) and the stomach being the next (7 cases; 30.4%). The large bowel was the site of the fewest (6 cases;26.1%). No esophageal lymphomas were encountered. The tumor was of male preponderance with the ratio of 2:1, and the lesions occurred most commonly in the 6th decade. Sixteen cases(69.6%) were diagnosed histologically as reticulum cell sarcoma, 5 (21.7%) as lymphocytic lymphosarcoma, and 2(8.7%) as hodgkin's disease. The diagnosis of primary lymphoma of the G.I tract was difficult to establish priorto surgical exploration. Clinical findings did not differ significantly from those of other G.I tract neoplasm. Roentgenographic studies were diagnostic of malignant tumor in 6 cases (86%) out of 7 gastric lymphoma with theremaining one also being suspicious of malignancy. Among those 6 gastric lymphoma, 3 cases were highly suggestiveof malignant lymphoma and in the remaining 3, carcinoma was suspected rather than lymphoma. In the small intestinethe diagnosis of neoplasm was made in 3 cases (60%) among 5 in which small bowel series and barium enema study were performed. The possibility of neoplasm was raised in another 30%. Roentgenograms of large intestine made the diagnosis of tumor in 75% of the cases in which X-rays were taken.