Doaa A M Esmaeil¹, Essam T Gaballah², Mohamed I Mourad³, Rehab Allah Ahmed ⁴ 1: Teaching Assistance, Faculty of Dentistry, Mansoura University, Egypt. 2: Professor of Oral Pathology and Vice dean of student and learning affairs, Faculty      of Dentistry, Mansoura University, Egypt. 3: Assistant Professor of Oral Pathology, Faculty of Dentistry, Mansoura University, Egypt. 4: Assistant Professor of Pathology, Faculty of Medicine, Mansoura University, Egypt. Abstract: Mucoepidermoid carcinoma is a common salivary tumor that affects both adults and children. CD-44 may be used as an indicator of aggressive behavior of some human malignancy. Multidrug resistance is one of the major obstacles for successful cancer chemotherapy.                     The present study was carried out for evaluation of the biological rules and the clinicopathological significance of Ki-67, CD-44 and MDR-1 expression in the different histopathological grades of MECs. Forty paraffin embedded MEC tissues were collected and classified to three groups according to their histological grades. Tissue sections were stained with Ki-67, CD-44 and MDR-1 then examined microscopically and analyzed statistically. High grade MEC cases showed the highest expression for Ki-67, CD-44 and MDR-1. From the findings of the present study, it can be concluded that Ki-67, CD-44 and MDR-1can be used to evaluate the degree of differentiation and to predict the prognosis of MECs, furthermore, high grade MEC cases with high proliferative indices might be resistant to chemotherapy