The nature and location of intermediate filament proteins (IFP) may provide new insights into the origin and differentiation of neoplastic cells. An immunofluorescent study of these IFP in a ease of a granular cell ameloblastoma revealed that all tumor cells contained the IFP keratin. Some granular cells, however, also contained the IFP vimentin, which is considered specific for mesenchymal tissues only. The implications of these observations are discussed. Study with monoclonal antibodies indicated the origin of the ameloblastoma from non‐keratinized squamous epithelium. A comparison of the anti‐keratin immunofluorescence pattern of the ameloblast‐like cells in the present tumor with ameloblasts in the tooth germ revealed no similarities, indicating that despite some resemblance of the peripheral columnar cells to ameloblasts, these cells differ in other as