A 70-year-old man admitted to a local hospital because of facial muscle weakness, tinnitus and facial pain in left side, was then given corticosteroid with a tentative diagnosis of Bell's palsy and his symptoms gradually improved. Since these symptoms recurred six months later, he was referred to our neurological service. As his brain CT revealed diffuse thickening and enhancement of the dura mater, he was thought to have hypertrophic pachymeningitis (HP). Intravenous antibiotics were started for aspiration pneumonia and his neurological symptoms gradually improved. HP caused by bacterial infection was thus likely and antibiotics, rifampicin and metronidazole, were administered orally as an outpatient. However, one month later, these symptoms were worsened with headache and double vision. He was then rehospitalized. MR imagings of the head with gadolinium disclosed diffuse meningeal thickening and enhancement, especially of the left-sided cerebellar tentorium. Erythrocyte sedimentation rate and C-reactive protein were moderately elevated. Serum angiotensin converting enzyme was within normal range. The test for cytoplasmic antineutrohil cytoplasmic antibody (ANCA) in the serum was negative, however, that for perinuclear ANCA was positive at a titer of 99 EU. Lumbar puncture showed normal findings and negative culture results for bacteria, fungi or mycobacteria. Dural biopsy specimens showed non-specific granulomatous inflammation of the dura with epithelioid histiocytes and Langerhans type multinuclear giant cells with caseous necrosis, however, with no presence of fungi or tubercle bacilli. After the oral administration of cyclophosphamide (100 mg, daily) and prednisolone (40 mg, daily), his neurological symptoms and laboratory findings have been gradually improved and he is well one year after discharge. This case together with previous reports suggests that ANCA positive HP without evidence of other organ involvements may belong to the limited form Wegener's granulomatosis. In the literatures of idiopathic HP, the treatment effect with corticosteroid alone is initially favorable, but transient. On the other hand, using the combined therapy of cyclophosphamide and prednisolone, the remission has been achieved in more than 90% of patients with WG. These data suggest that P-ANCA positive HP should be treated with a combination of corticosteroid and cyclophosphamide.