Magnetic resonance imaging in the evaluation of spinal tumors. Magnetic resonance imaging (MRI), which has recently begun to replace myelography, postmyelography computed tomography (CT), and to some extent, bone scans, has become the procedure of choice in the evaluation of spinal tumors; the applications of MRI in this role are reviewed. In the extradural space, MRI is the most sensitive technique for the detection of tumors in the vertebral bodies. At the same time, it provides superb delineation of suspected thecal sac impingement. In the intradural extramedullary space, MRI is generally as accurate as myelography and postmyelography CT while being noninvasive. Finally, in the intramedullary space, MRI is unquestionably the procedure of choice in the evaluation of suspected cord tumors. In general, MRI has become the best initial procedure in the evaluation of suspected tumors of the spine, regardless of the space in which they may lie; frequently, it is the only required examination. 