Activation of the complement cascade plays an important role in the pathogenesis of postinfectious glomerulonephritis. We report successful terminal complement pathway blockade using an anti-C5 monoclonal antibody (eculizumab) in an 8-year-old child with severe acute postinfectious glomerulonephritis requiring hemodialysis. The child presented with clinical, serologic, and histopathologic criteria for diffuse crescentic postinfectious glomerulonephritis. Complement measurements showed low C3 and C4 levels, with increased SC5b-9 titers.