Immune reconstitution inflammatory syndrome (IRIS) encompasses a variety of conditions that occur among HIV-infected patients in a temporal relationship with increases in CD4 cell count as a result of highly active antiretroviral therapy (HAART). Most conditions associated with IRIS are infectious. Malignancies, such as Kaposi's sarcoma, have also been reported. We report a case of sinusitis with presumptive inflammatory pseudotumor as a manifestation of IRIS that occurred 20 weeks after the initiation of HAART.