Immunofluorescent and immunoperoxidase labelling of normal and metaplastic human submandibular salivary glands with a battery of cytokeratin-specific monoclonal antibodies was carried out. Labelling with a broad spectrum cytokeratin antibody (KG 8.13), as well as with antibody to cytokeratin polypeptide No. 18 (Ks 18.18) was observed in all the epithelial elements of the gland. Polypeptide No. 19, however, was present in ductal cells only, sparing the acini and the associated myoepithelium. Antibody KS 8.58, specific for cytokeratins Nos. 13 and 16, selectively labelled basal cells along the large ducts. Examination of squamous metaplasia associated with chronic suppurative sialadenitis indicated that the metaplastic cells display the same cytokeratin profile as the normal ductal cells and are not labelled with antibodies KS 8.58 and KK 8.60 which usually stain normal and pathological stratified epithelia. The significance of these observations for the histogenesis of normal salivary glands, as well as for the development of the metaplastic process, is discussed.