The pathogenesis of allergic fungal rhinosinusitis (AFRS) is thought to represent an immunological reaction to fungal antigens. Recent studies have implicated superantigens and non-immunoglobulin E (IgE)-mediated mechanisms in the development of AFRS. The objective of this study is to assess the prevalence of Staphylococcus aureus in AFRS vs other subsets of chronic rhinosinusitis with polyps (CRSwNP, also termed non-AFRS). A case series with retrospective review of 19 patients with AFRS and 21 patients with CRSwNP was performed at a tertiary referral center. The diagnosis of AFRS required the presence of defined criteria described by Bent and Kuhn. Bacterial cultures and fungal cultures were analyzed for each group. S. aureus was significantly more prevalent in the AFRS group compared with the non-AFRS group (63.2% vs 24.1%, p = 0.005). S. aureus has been implicated as a disease modifier in CRSwNP through superantigen-mediated mechanisms. This study demonstrates a higher prevalence of S. aureus in patients with AFRS vs patients with other subsets of CRSwNP (non-AFRS). These results support a potential role for S. aureus in the pathogenesis of AFRS. © 2013 ARS-AAOA, LLC.