A case of granular cell ameloblastoma was studied by light and electron microscopy. Histologically, the lesion resembled simple ameloblastoma, but differed from the latter in that it contained many cells with granular eosinophilic cytoplasm. Ultrastructurally, the cytoplasmic granules were identified as lysosomes. These organelles were particularly abundant in cells situated in the center of islands and clusters of neoplastic cells. Since no cytoplasmic components could be identified in any of these lysosomes, it was concluded that they are not engaged in autophagy or in remodeling of the neoplastic cells.