Here we present a 53-year-old woman with rheumatoid pachymeningitis. The subject had rheumatoid arthritis (RA) for 15 years. In April, 1996 she began to experience intermittent headaches. In September, her headaches became severe and continuous. In October, she suddenly developed ptosis of the left eye and diplopia. She also started to have dysphagia and she found it increasingly difficult to eat. She was admitted to our hospital on November 1, 1996. Neurological examinations revealed palsies of the left IIIrd, IVth, and VIth, and bilateral IXth, and Xth cranial nerves. Laboratory findings showed leukocytosis, elevated blood sedimentation rate, and positive CRP. Serum RA titer was positive (30x). The cerebrospinal fluid was normal and bacteriological examination was negative. T1-weighted MRI demonstrated hypertrophic cranial dura extending from the falx cerebri to tentorium cerebelli, which was enhanced markedly by Gd-DTPA. The dura adjacent to the cavernous sinus and the clivus were also thickened, which probably caused her cranial polyneuropathies. The dural biopsy showed massive infiltration of the inflammatory cells throughout the dura, proliferation of collagen fibers, and necrotic granuloma with neutrophilic infiltrations. Neither rheumatoid nodules, nor vasculitis were found. Despite the absence of rheumatoid nodules in the dural biopsy, the clinical features, pathologic specimens, and MRI findings of the thickened dura were most consistent with rheumatoid pachymeningitis. Administration of dexamethason ameliorated her headache on the 4th hospital day, and the cranial polyneuropathies completely disappeared on the 35th hospital day. The dural enhancement previously seen on the contrast T1-weighted MRI was diminished. Serum RA titer was also normalized (10x). Rheumatoid pachymeningitis is an extremely rare disease, and only 16 cases were reported in the literatures. Hypertrophic pachymeningitis should be considered as a diagnostic possibility in RA patients who have prolonged headache, and Gd-DTPA MRI is recommended to demonstrate the dural involvement.