Over the past decade cyclophosphamide has come to assume an increasingly prominent role in the management of severe, life-threatening manifestations of SLE. Intermittent, intravenous pulse cyclophosphamide has become the standard of treatment of diffuse proliferative lupus nephritis (WHO Class IV), and there is now substantial clinical literature to suggest an indication for intermittent cyclophosphamide therapy in most other forms of serious lupus affecting major organ systems, in particular lupus vasculitis and acute central nervous system manifestations. This update reviews the use of cyclophosphamide in the management of lupus nephritis, expands on its role in other manifestations of SLE, and discusses potential complications of the drug.