Six hundred fifty outpatients with rheumatoid arthritis (RA) were evaluated and followed up during a 7-year period. As part of their routine evaluation or because of neck-shoulder girdle symptoms, 48% of the patients underwent routine cervical spine radiography. Sixty-one RA patients (9% of the total population) had C 1 4 2 involvement. Compared with the 589 patients with no evidence of Cl-C2 involvement, these 61 patients were significantly more likely to be younger, female, and seropositive, and they had significantly more nodules and erosions, as well as a longer disease duration. Based on radiographic evidence of C 1 4 2 disease severity, 3 groups emerged. Group 1 (28 patients) had lateral mass collapse, group 2 (27 patients) had lateral facet joint sclerosis, erosion, or loss of joint space with no collapse, and group 3 (6 patients) had lateral subluxation with no bone or cartilage changes. Nine patients in group 1 had severe pain, and 25 had a nonreducible rotational tilt of the head. None of the patients in the other 2 groups had either of these signs or symptoms. Moreover, patients in group 1 were more likely to have other C 1 4 2 or subaxial subluxations and were more likely to have myelopathy. C 1 4 2 lateral facet joint involvement is common in RA, correlates with disease severity generally and specifically with that in the cervical spine, and, when severe, causes nonreducible rotational tilt of the patient's head.