Expression of c-erbB-2 oncogene and mutant p53 protein were detected immunohistochemically in 14 cases of myoepithelioma and 6 cases of myoepithelial carcinoma of the salivary gland. Five of the 6 myoepithelial carcinomas and nine of the 14 myoepitheliomas were overexpression of c-erbB-2 oncoprotein. The salivary ductal epithelial cells near tumors were overexpression of c-erbB-2 oncoprotein. These results indicate that c-erbB-2 may be an initial oncogene during the histogenesis of myoepithelial tumors. The p53 protein was positive in five cases of the 6 myoepithelial carcinoma, whereas all myoepitheliomas were negative. The results indicate that the mutant p53 gene may play an important role in the carcinogenesis of myoepithelial carcinoma.