The etiology of allergic fungal rhinosinusitis (AFRS) remains controversial. Initially thought to represent an immunoglobulin E (IgE)-mediated hypersensitivity to fungal antigens, additional data have implicated other non-IgE and cellular-mediated pathways. The aim of this study was to characterize T-helper type 1 (Th1) and Th2 immune responses of blood lymphocytes from AFRS patients by fungal antigen stimulation to help differentiate these possible pathways. Peripheral blood mononuclear cells (PBMCs) isolated from AFRS patients (n = 10) and healthy controls (HCs; n = 11) were exposed to four different fungal extracts (Alternaria, Aspergillus, Cladosporium, and Penicillium) in duplicate. After a 72-hour incubation, the supernatants were analyzed for cytokine levels of three Th1 (interferon [IFN] gamma, interleukin [IL]-2, and tumor necrosis factor alpha) and three Th2 (IL-10, IL-5, and IL-4) cytokines by cytometric bead array flow cytometry. Serum fungal-specific IgE levels were measured by ImmunoCAP (Pharmacia Diagnostics, Kalamazoo, MI). Fungal extracts of Alternaria and Cladosporium stimulated higher levels of IL-5 from PBMCs in AFRS when compared with HCs (p < 0.05). IL-4 was also elevated for Alternaria in AFRS versus HCs (p < 0.05). A skewed Th2 response to fungal antigen exposure was confirmed by an elevated IL-5/IFN-gamma ratio in AFRS subjects (p < 0.05). Initial studies suggest a correlation between percent T-cell activation and IL-5 expression to IgE levels. Fungal antigens stimulated a notable but not statistically significant increase in IL-10 response in HCs. In AFRS patients, fungal antigens stimulated T-cell activation, inducing a predominantly Th2 immune response. Healthy controls expressed an inhibitory cytokine IL-10 when exposed to these fungal antigens, possibly serving as a protective response.