We evaluated the efficacy of granulocytaperesis and leukocytapheresis for the treatment of rapidly progressive glomerulonephritis (RPGN) and lung hemorrhage caused by microscopic polyangiitis. Three patients with RPGN were treated by granulocytapheresis (GCAP) and five patients with RPGN were treated by leukocytapheresis (LCAP). The prednisolone dose was 0.4 +/- 0.2 g/kg/day (mean +/- SD; range 0.2-0.8 g/kg/day). Pre-treatment serum creatinine was 3.2 +/- 1.4 mg/dL (1.4-5.1 mg/dL). The patients were followed for a mean period of 15 +/- 6 months (6-23 months). Renal function improved in five of the eight RPGN patients. Three lung hemorrhage episodes in two different patients were treated with GCAP and one lung hemorrhage episode was treated with LCAP combined with various doses of corticosteroids. All four lung hemorrhage episodes were ameliorated. We concluded that combined therapy of GCAP or LCAP and corticosteroids is effective for the treatment of RPGN and lung hemorrhage due to microscopic polyangiitis.