Crescentic glomerulonephritis is a severe form of glomerular injury that is characterized by disruption of the glomerular basement membrane, cellular proliferation within Bowman space, and (often) fibrinoid necrosis. Pauci-immune crescentic glomerulonephritis, so called because it involves little or no glomerular immunoglobulin deposition, is one of the most common causes of rapidly progressive glomerulonephritis. In the majority of patients, pauci-immune crescentic glomerulonephritis is a manifestation of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. However, some patients with pauci-immune crescentic glomerulonephritis lack ANCAs. This Review compares the prevalence, clinical manifestations, histopathology, and outcomes of ANCA-negative pauci-immune crescentic glomerulonephritis with those of ANCA-positive disease. We also discuss the possible pathogenesis of ANCA-negative pauci-immune crescentic glomerulonephritis, paying particular attention to the mechanisms and role of neutrophil activation.