A 56-year-old female developed rapidly progressive glomerulonephritis in the course of myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-associated pachymeningitis that had been found four years previously. On admission, her serum creatinine increased from 0.8 mg dL to 1.84 mg dL and to 3.66 mg dL every 3 to 4 weeks. Urinalysis revealed that urinary protein excretion was 1.25 g day and 3+ hematuria. MPO-ANCA titer was found to be 50 EU and anti-glomerular basement membrane (GBM) antibody was also elevated to as high as 174 EU. Renal pathology revealed cellular to fibrocellular crescents in 21 out of 23 glomeruli with interstitial inflammation and fibrosis. Immunohistochemistry with anti IgG antibody showed linear staining along the glomerular capillary walls. Following plasma exchange and methylprednisolone pulse therapy, oral prednisolone at a dose of 50 mg day was instituted, but without significant effect. Subsequent cyclophosphamide pulse therapy was effective, resulting in the stabilization of serum creatinine at 2 mg dL and disappearance of urine abnormalities. In addition, the MPO-ANCA titer and anti-GBM antibody titer of the patient decreased to within the normal range in one month and three months, respectively. Pulmonary lesions were not found throughout the course. Recently the emergence of anti-GBM antibody-associated crescentic glomemrulonephritis in the course of MPO-ANCA-associated vasculitis has increasingly been reported. Accumulation of such cases may unravel the pathogenesis of these diseases. one month and three months, respectively. Pulmonary lesions were not found throughout the course. Recently the emergence of anti-GBM antibody-associated crescentic glomemrulonephritis in the course of MPO-ANCA-associated vasculitis has increasingly been reported. Accumulation of such cases may unravel the pathogenesis of these diseases.