This patient is the only reported case of concomitant mixed tumors of the parotid and contralateral submaxillary gland. Each lesion had histologic changes consistent with different stages in the transformation of a benign to a malignant mixed tumor. Identifying premalignant disease in the parotid tumor and early preinvasive carcinoma in the submaxillary tumor lends support to the concept of malignant progression in salivary gland mixed tumors.