We retrospectively analyzed the Magnetic Resonance (MR) imaging findings in 41 cases of histologically proved malignant tumors of oral cariey. The diagnositic value of MR imaging in detection and delineation of the lesions was assessed. the value of MRI was xompared with that of computed Tomography (CT) in 14 patients. Thirty-four cases of 41 malignant tumors were squamous cell carcinomas. Adenoic cystic carcinomas (2 cases), non-Hodgkin lymphomas (2 cases) and mucoepidermoid carcinoma (1 case) were also included in this study. Most of the lesions were isointense or slightly hyperintense to muscle on T1 weighted images and showed variable degrees of high signal intensity of T2 weighted images. Two cases of malignant melanomas showed characteristic hyperintensity on T1 weighted images. T2 weighted image was better in detection and delineation of tumor in most of the cases. In 6 cases, Gd-DTPA-enhanced T1 weighted image was better than T2 weighted image. T2 weighted image was useful for the evaluation of deep tissue infiltration and T1 weighted image was useful for the evaluation of bone invasion and superficial tissue infiltration and T1 weighted image was useful for the evaluation of bone invasion and superficial tissue plane invasion. The lesion was detected only by MR in 3 cases of 14 in which CT was also performed. Mr imaging was more sensitive in the evalustion of bone marrow involvement. MR imaging is very useful modality in evaluating oral cavity malignany and is superior to CT in delineation of the tumor as well as in the evaluation of mandible invasion.