This paper presents 191 cases of malignant lymphoma of the Waldeyer's ring. It comprised 21% of all the malignant lymphomas diagnosed in our hospital, 1964-1989, and ranked first in the extranodal malignant lymphomas. The locations of these tumors were: tonsil (in 127 cases), nasopharynx (in 62) and base of tongue (in 2). Cervical lymph nodes were frequently involved. Thirty cases, including polymorphic, clear cell and lymphoblastic lymphomas, were examined by PAP immunohistochemical method and were all shown to be of T-cell type. Owing to the bizarre appearance of the tumor cells, varied histological architecture and diverse modes of invasion they were often misdiagnosed as anaplastic or poorly differentiated carcinoma. Malignant granuloma was also one of the diagnostic problems because of the ulcer formation. Occasionally, as the tumor base was infiltrated by large amount of inflammatory cells, they could also be misdiagnosed as inflammatory lesions. Consequently, we believe that the immunohistochemical method should be considered as an important supplementary method of diagnosis.