A case of primary amyloidosis diagnosed by morphological and immunological examination was reported. The patient was a 71 year-old woman who had tumorous masses at the retromolar pad, the left buccal mucosa and the tongue. The specimens taken from the lesions displayed green birefriegence after Congo red staining on polarization microscopy, and proliferation of plasma cell around the amyloid substance was obsereved. Also, positive reaction of λ type antisera with those cells, as well as the amyloid substance were shown by immunohistochemical method. Besides, the quantitative analysis of immunogloblin and immunoelectrophoresis of the patient's serum wre examined; increased IgGλ type monoclonal protein was revealed. However, there were no findings associatedwith multiple myeloma by several systemic examinations, e. g., X-ray and Tc-scintigram. From those findings described above, this case was finally diagnosed as “primary amyloidosis with plasma cell dyscrasia”.