Rheumatoid pachymeningitis is a rare complication of rheumatoid arthritis. This disease was confined to the dura and pia-arachnoid of the lumbar cord in our patient. Her neurologic deficits responded to surgical decompression and corticosteroid therapy. Radiologic evidence and the differences in cell count, protein, and glucose content between lumbar and cisternal cerebrospinal fluid indicate that rheumatoid pachymeningitis can be localized to a discrete region of the central nervous system. Elevated immunoglobulins, IgM and IgG rheumatoid factors, low molecular weight IgM, and immune complexes were found in the cerebrospinal fluid and implicate an immune reaction in the pathogenesis of this disease, which is probably similar to inflammatory processes involving other organs in rheumatoid arthritis.