Context .- A number of entities may result in necrosis in the sinonasal tract and lead to significant morbidity and mortality. These include infections, necrotizing vasculitis, neoplastic processes, and drug dependency. This review will concentrate on the differential diagnosis of sinonasal necrotizing lesions. Objective .- To review the differential diagnoses of necrotizing destructive lesions of the sinonasal tract. Data Sources .- The current literature was reviewed to provide updated information regarding the differential diagnosis of sinonasal necrotizing lesions, including infectious disease processes; antineutrophilic cytoplasmic antibody-associated vasculitides; neoplastic processes, particularly natural killer/T-cell lymphomas; and drug abuse. Conclusions .- The differential diagnosis of necrotizing sinonasal lesions is broad, with often overlapping diagnostic features that lead to diagnostic challenges. Ancillary tests such as special stains and immunohistochemical studies can offer significant assistance.