The effect of plasmapheresis (PP) monotherapy and PP with corticosteroid administration were evaluated in a male with crescentic glomerulonephritis (CrGN). On the first admission, since he was positive for both anti-neutrophil cytoplasmic myeloperoxydase autoantibody (MPO-ANCA) and circulating immune complex (IC), the treatment was started with PP alone to reduce these autoantibodies immediately. During two months, three series of PP were performed : three sessions of plasma exchange (PEX) with fresh frozen plasma (FFP), two sessions of double filtration plasmapheresis (DFPP), and then, another two sessions of PEX, respectively. ANCA remained suppressed for 4 weeks after the first series of PEX, and increased thereafter. Subsequent DFPP caused a rebound of ANCA titer while the second PEX suppressed ANCA, at least, for 1 week. Though creatinine clearance (Ccr) improved after the first PEX and this level was maintained, ANCA increased again after the second PEX. Therefore the patient was treated with methyl-prednisolone (m-PSL) semipulse therapy followed by mild cocktail therapy including prednisolone (PSL) at 20 mg/day and mizoribine at 100 mg/day. In two weeks, ANCA and IC became negative and Ccr improved further. When PSL was tapered off, the ANCA became positive again. Since ANCA was not suppressed and Ccr declined gradually even after re administration of oral PSL at 30-40 mg/day, PP was superimposed on steroid therapy with 3 sessions of DFPP and PEX, respectively. Ccr was improved, but ANCA was not sufficiently decreased by DFPP. Subsequent PEX was more efficient than DFPP in reducing the ANCA level. However, m-PSL semipulse was eventually required for complete suppression of ANCA. Thus PP was partially effective, but not sufficient as monotherapy. However it was considered advantageous as an adjunct therapy to reduce the dose of immunosuppressive drugs in CrGN. As to the mode of PP, PEX with FFP appeard to be more effective than DFPP in reducing the plasma ANCA level.