Clinicopathological study was performed in 15 resected cases of gastric malignant lymphoma. The clinicopathological features were as follows. 1) In 6 of 15 cases, the tumor was located in the upper part of the stomach. 2) Lymph node metastasis was observed in 5 of 12 cases. 3) In 3 of 15 cases, multiple tumorous lesions were noted. We also studied the relationship between PCNA expression and clinical prognosis in 10 cases, specimens of which were well preserved, out of 15 cases. About 500 nuclei immunohistochemically stained by PCNA monoclonal antibody were counted, and results were expressed by positive cell ratio (PCNA labelling index LI%). In conclusion, 1) the positive cases of lymph node metastasis showed a tendency for PCNA LI to increase compared with the negative cases. 2) The recurrent cases showed a tendency for increased PCNA LI compared with the cases without recurrence. 3) Cases with more than 60% of PCNA LI tended to have a poor prognosis compared with those of less than 60%.