This study proposes a simple method for assessing whether non-respiratory epithelia of the nasopharynx (i.e. cuboidal, squamous) represent a modified differentiation from the normal pseudostratified lining, or whether they possess common characteristics suggesting they are just in a different morphological stage. Peroxidase-labelled lectins were used, since they detect sugar residues of membrane glycoconjugates which play an important role in cell differentiation. Biopsies were taken from healthy controls and from patients affected by upper airway inflammation of varying degree and duration. While pseudostratified and cuboidal epithelia possess similar histochemical characteristics, squamous epithelium has a different behaviour; in particular it is the only type to show intense reactivity to Lotus tetragonolobus lectin (LTA). This would seem to indicate that squamous epithelium is in a different state of differentiation, possibly suggesting dysplasia. Lectins may be valuable both in morphological studies and in the clinical evaluation of airway epithelia.