Calretinin is a calcium-binding protein with molecular weight of 29 kDa (KiloDalton). It is expressed in a variety of normal and tumorigenic tissues. Its expression in odontogenic epithelium during odontogenesis and in neoplastic odontogenic tissues has been demonstrated. This study was undertaken to evaluate the expression of Calretinin in a group of odontogenic cysts and tumors. The expression of Calretinin was evaluated immunohistochemically in 42 samples including 8 cases of periapical cyst, 7 cases of dentigerous cyst, 7 cases of keratocystic odontogenic tumor, 8 cases of solid (multicystic) ameloblastoma, 6 cases of unicystic ameloblastoma and 6 cases of adenomatoid odontogenic tumor. Positive immunohistochemical reaction was found in all cases of solid ameloblastoma (100%), in 4 cases of unicystic ameloblastoma (67%) and 4 cases of keratocystic odontogenic tumors (57%) whereas none of the other odontogenic cysts and adenomatoid odontogenic tumors included in this study showed reactivity. Intensity was higher in the ameloblastomas compared with the keratocystic odontogenic tumors. On the basis of these results, it is suggested that calretinin might be used as a specific immunohistochemical marker for the ameloblastomas and could play an important role in the differentiation of aggressiveness of different odontogenic tumors.