Two cases of oral B-lymphomas with numerous Russell body-like inclusions are described. One occurred primarily in the hard palate of a 59-year-old female with Sjögren's syndrome, and was diagnosed as lymphoplasmacytoid immunocytoma by Kiel's classification. The other occurred secondarily in the buccal mucosa of a 44-year-old female whose first affected site was orbital soft tissues, and was diagnosed as extramedullary plasmacytoma. The diagnostic problems and the nature of the Russell body-like inclusions are discussed based on the immunoperoxidase (PAP) method and electron microscopic study. The first patient is well without recurrence 19 months after surgery, while the second patient developed extramedullary plasmacytoma in the abdomen 5 months after surgery for the buccal plasmacytoma.