OBJECTIVE Our study goal was to study fungus-specific immunoglobulins G (sIgG) and E (sIgE) in polypoid rhinosinusitis with and without evidence of allergic fungal rhinosinusitis (AFS). METHODS A prospective analysis was conducted of fungal sIgG and sIgE using a 9-mold RAST panel in 13 AFS, 11 AFS-like, and 27 non-AFS polypoid rhinosinusitis patients. Nonpolyp controls included 17 volunteers with allergic rhinitis and 11 with no atopic history. RESULTS All groups had elevated fungal sIgG levels. Polyps, increasing polyp severity, and AFS were associated with elevated fungal sIgG to a greater number of molds. The AFS group had sIgE elevations (>or=class II) to an average of 5 molds versus only 0.1 in the non-AFS polyp group. Total IgE was 971 U/mL versus 64 U/mL, respectively. CONCLUSIONS Multiple elevations of fungal sIgE are adequate diagnostic evidence of these fungi when fungal cultures and histologic examinations are negative in diagnosing AFS. The significance of increased fungal sIgG remains unclear. CONCLUSIONS Early recognition of AFS may be facilitated by screening polypoid rhinosinusitis patients with total serum IgE and RAST testing.