The present trial, CYCLOPS, aims to reduce the cumulative exposure to immunosuppressive drugs by administering cyclophosphamide (CYC) as intermittent pulses. The potential benefit of using CYC in this way for AASV has been demonstrated in preliminary, smaller studies. Patients with previously untreated AASV and, “generalised”, but not life threatening, disease with renal involvement, will be randomised to either continuous oral CYC or intermittent pulse CYC. CYC will be continued until three months after remission has been achieved, with a minimum CYC total duration of six months and maximum duration of twelve months; both limbs will then receive the same maintenance regimen of azathioprine and prednisolone.