The role of atopy to aeroallergens in chronic rhinosinusitis without nasal polyps (CRSsNP) remains unclear. This study aimed to investigate the mucosal immunopathologic characteristics of CRSsNP with and without atopy to inhalant allergens. Methods: Thirteen nonatopic CRSsNP patients, 9 atopic CRSsNP patients, and 11 nonatopic control subjects were enrolled in this study. The expression of type 1, 2, and 17 cytokines, growth factors, and chemokines for T cell subsets and granulocytes in sinonasal mucosa was detected using Bio-Plex suspension chip technology or enzyme-linked immunosorbent assay (ELISA). Subjective symptoms were scored on a visual analogue scale (VAS), while disease severity on computed tomography (CT) was graded by the Lund-Mackay CT scoring system. Results: There was no significant difference in VAS and CT scores between atopic and nonatopic CRSsNP. Compared with control, both atopic and nonatopic CRSsNP demonstrated increased interferon gamma (IFN-gamma) levels in sinonasal mucosa. In contrast, although no difference in interleukin 5 (IL-5), IL-13 and eotaxin-1 expression, or mucosal eosinophil infiltration, was found between the control and whole CRSsNP group, atopic CRSsNP manifested an increased expression of IL-5, IL-13 and eotaxin-1, as well as an enhanced infiltration of mucosal eosinophils in comparison with control and nonatopic CRSsNP. Mucosal eosinophil infiltration correlated with IL-5 and eotaxin-1 expression. No difference in IL-12, IL-4, IL-6, IL-17A, IL-8, myeloperoxidase, "regulated upon activation normal T cell expressed and presumably secreted" (RANTES), or chemokine (C-X-C motif) ligand 10 (CXCL10) protein expression was found among control, atopic CRSsNP, and nonatopic CRSsNP. Conclusion: Atopic and nonatopic CRSsNP have distinct mucosal immunopathologic profiles. CRSsNP is a heterogeneous disorder consisting of multiple groups of biological subtypes, or "endotypes,"which may argue for different therapeutic strategies. (C) 2016 ARS-AAOA, LLC.