Tyrosine-rich crystalloids are described in an example of an adenoid cystic carcinoma arising in an oral minor salivary gland of the hard palate. This represents the first reported case of an adenoid cystic carcinoma of oral minor salivary gland in which tyrosine-rich deposits have been identified. The tyrosine deposits appear refractile but not birefringent at the light microscopic level; and histochemical findings indicate a relatively simple, homogeneous chemical composition rich in tyrosine. Their ultrastructural nature is that of a finely granular, but otherwise patternless, highly electron-dense material. The electron microscopic features of the neoplasm are similar to previous reports. Based upon the findings of this and previous investigations, it is not as yet possible to state whether the tyrosine-rich deposits truly represent a crystalline or amorphous solid.