Current treatment based on the use of cyclophosphamide and corticosteroids has changed anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides from highly fatal into more ch ronic relapsing diseases. Relapses are a major problem in these diseases and cause increased morbidity and mo rt alit y. Current clinical re sea rc h mainly focuses on achieving control of active disease while minimizing treatment-related toxicity. Risks for longterm relapse and their sequelae have been less thoroughly studied. It is noteworthy that, besides treatment, several other factors have been associated with the occurrence of relapses. Thus, compared to MPO-ANCA positive patients, patients with PR3-ANCA associated vasculitis run a significantly increased risk of experiencing relapses. ANCA-status during follow-up, levels of T cell activation, genetic background, and infectious and other exogenous factors have been linked to relapse as well. With a few exceptions, these associations are merely descriptive and not pathophysiologically proven. Furthermo re, data on adapting treatment in accordance with risk factors for relapse are scarce. We review here the risk factors for relapse in ANCA-associated vasculitis, their potential pathogenic implications, and their possible role in p reventive strategies and adaptations of current treatment policies.