A review was made of the clinical histories, treatment, and renal histologic features of 12 patients with anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM disease). Two patients had milder histopathologic changes in their kidney biopsy specimens and achieved clinical remission. The other ten patients with severe lesions in their biopsy specimens progressed to renal failure. In addition, vascular lesions of thrombotic microangiopathy were present in six of 12 patients. Six patients had clinical laboratory evidence of microangiopathic hemolytic anemia. There are two important points to be noted from this study. First, the kidney biopsy specimen may be a useful indicator of disease severity and prognosis. Second, clinical laboratory or histologic evidence of thrombotic microangiopathy may occur in 75% of patients with anti-GBM disease.