We present a patient with Morbus Wegener and crescentic glomerulonephritis. Treatment with cyclophosphamide and prednisolone resulted in the disappearance of signs and symptoms of systemic inflammation. However, renal function deteriorated. Renal biopsy showed evidence of continuing capillary necrosis. Renal function improved with added plasmapheresis treatment. This case report illustrates that in patients with vasculitis necrotizing glomerulonephritis may remain active despite immunosuppressive therapy, even in the absence of extrarenal disease activity.