Granulomatosis with polyangiitis is a common form of small-vessel vasculitis, remarkable for its tendency toward multisystem manifestations. Standard induction treatment calls for the use of low-dose daily cyclophosphamide (CYC) and glucocorticoids. Treatment goals for newly diagnosed patients include increased survival, induction of remission, reduction of relapse frequency, and minimization of treatment toxicity. Induction and maintenance treatments with CYC, glucocorticoids, and other immunosuppressive therapies improve the disease course, but relapse- and treatment-related toxicity and infections demand consistent, patient-specific monitoring.