Ectopic production of human chorionic gonadotropin (HCG) in tumor cells is an uncommon phenomenon that has rarely been documented. The immunoperoxidase method was used to demonstrate the presence of beta-subunit of HCG in malignant lymphoma cases, using paraffin-embedded sections of lymph nodes. 3 of 11 cases of malignant lymphoma (27%) were positively stained with beta-subunit of HCG. All positive cases were T-cell type malignant lymphomas, but all adult T-cell leukemia lymphoma cases did not react with HCG. All B-cell type malignant lymphoma cases were not stained by HCG. Hence, this evidence suggested that beta-subunit of HCG may be useful as a tumor marker in certain malignant lymphoma patients. To the best of our knowledge, production of beta-subunit of HCG in the cytoplasm of malignant lymphoma cells has not been reported.