To explore the expression of proliferating cellnuclear antigen (PCNA) and tumor suppressor gene P53 product in mucoepidermoid carcinoma of the salivary glands, we studied 41 cases by immunohistochemical method. All of the cases were PCNA positive. The positive index, distribution pattern and cellular staining intensity for PCNA expression were correlated with carcinoma grade. P53 protein expression was found in 17 (41.5%) of the 41 cases; among them the expressions were weak in 9 cases. These results indicate that positive index, distribution pattern and cellular staining intensity of PCNA expression may be served as an indicator for evaluating the differentiating degree of the tumor.