Non-Hodgkin's lymphoma (NHL) is a frequent complication of human immunodeficiency virus (HIV) infection, but involvement of the sinonasal region has only rarely been reported. We report three cases of AIDS-associated sinonasal NHL that occurred at our institution and review eight cases that were reported in the literature. The epidemiological and clinicopathologic features of these cases are described and compared with those of three other groups of patients: non-HIV-infected patients with sinonasal NHL, HIV-infected patients with NHL of any anatomic site, and HIV-infected patients with infectious sinusitis. Patients with AIDS-associated sinonasal NHL more frequently developed bony erosion and presented with signs and symptoms referable to adjacent structures, such as the orbit, than did HIV-infected patients with sinusitis, and patients with AIDS and NHL less frequently had typical sinus symptoms and diffuse sinus involvement than did patients with sinusitis. However, the clinical manifestations of these conditions overlap; thus a high index of suspicion for NHL is imperative for prompt diagnosis. These lymphomas typically are high-grade and disseminate early, and the prognosis is generally poor.