Amelogenins, enamel proteins in odontogenic tumours, were detected immunohistochemically using a monoclonal antibody. They were strongly expressed in amyloid-like material, ghost cells, and the cells surrounding ghost cells of calcifying epithelial odontogenic tumours and cysts, whereas calcified bodies within the tumours and cysts showed negative staining. The expression of amelogenins was also positive in tumour cells of ameloblastoma, adenomatoid odontogenic tumour, squamous odontogenic tumour and ameloblastic fibroma. Peripheral tumour cells of the follicular ameloblastoma were positive with relatively intense staining. Undifferentiated or flattened tumour cells of adenomatoid odontogenic tumour and non-keratinized tumour cells of the squamous odontogenic tumour showed marked staining. Reduced ameloblasts in the odontoma displayed the strongest staining for amelogenins. The study suggests that biosynthesis of amelogenins may occur in the homogeneous materials of calcifying epithelial odontogenic tumours and cysts.