Fifteen patients with classic rheumatoid arthritis were investigated with plain films, pluridirectional tomography, and surface-coil T1-weighted MR imaging at 500/17 (TR/TE). We evaluated the atlantodental interval; basion-dental interval; density or intensity of the dens; dens erosion; cranial settling; anterior, posterior, lateral, or rotatory atlantoaxial subluxation; subaxial subluxation; ligamentous calcification or osteophytes; erosion; cystic changes; joint-space narrowing of the apophyseal articulations; and posterior spinous process erosion. In addition, the cervicomedullary angle and the neuraxis configuration were identified on MR images. To determine its normal range, the cervicomedullary angle was measured in 50 patients whose MR studies were unrelated to the craniovertebral junction. All patients with a cervicomedullary angle less than 135 degrees had evidence of brainstem compression, cervical myelopathy, or C2 root pain. Also, all patients with cervicomedullary junction compression were neurologically abnormal. MR was found to be as good as tomography in evaluating the atlantodental interval, dens erosion, ligamentous calcification or osteophytes of the upper spine, subaxial subluxation, and various subluxations that occur in the occiput-C2 area. MR was less effective than tomography in evaluating the basion-dental interval, erosion of the posterior spinous processes, apophyseal joint disease from C3 inferiorly, and cystic changes of the articular facets of C1-C2. The most clinically important parameters were well seen with MR. The data show that MR is an excellent imaging procedure for evaluating rheumatoid arthritis of the cervical spine.