In this prospective study of 31 patients, the most sensitive assessment of malignant invasion of the mandible was by physical examination. Bone scanning and conventional roentgenographs are useful adjuncts in the staging evaluation of patients when clinical involvement is suspected and to determine the extent of disease in order to aid in treatment planning. However, they are frequently subject to false-positive interpretive errors, especially due to increased osteoblastic activity associated with dental disease and occasional tumor adjacent to the mandible. When appropriate, the radiographs ordered should be those that allow for the most accurate assessment of the particular lesion as determined by its location. Until a more specific and accurate method for detecting and measuring malignant invasion of the mandible is developed, the physical findings and the judgment of the head and neck surgeon remains our most valuable tool.