Wegener granulomatosis involves both the respiratory and genitourinary systems. Kidney lesions are invariably focal. Wegener granulomatosis only rarely affects other genitourinary organs and, until now, has not been described as a mass in the kidney. In the case presented, the diagnosis was unknown before surgery, though clinically suspected. The management, which included nephrectomy and chemotherapy with cyclophosphamide (Cytoxan) and prednisone, caused a marked improvement, and the patient was discharged in stable condition.