Allergic fungal sinusitis is a newly recognized entity consisting of a pansinusitis with allergic mucinous infiltrates in all involved sinuses. The disease process itself is very different from all other types of rhinosinusitis. Pathophysiologically the disease is a combination of both IgE-mediated and antibody-antigen reactions to the specific fungal antigens. Here we present two cases of allergic fungal sinusitis--one caused by Curvularia lunata species (an ubiquitous soil fungi), another caused by Alternaria. Only one other case of allergic fungal sinusitis caused by curvularia in which extensive immunologic testing was done has appeared in the literature. No reports of alternaria causing allergic fungal sinusitis have appeared in the literature. Diagnostic criteria for allergic fungal sinusitis include radiologic evidence of pansinusitis in an atopic individual; findings at surgery of allergic mucin; positive fungal cultures; and specific immunologic testing, including both humoral and cellular arms of the immune system. Treatment options for allergic fungal sinusitis are discussed and include surgery alone, surgery and steroids, or steroids alone. The role of allergy immunotherapy injections remains to be defined. In general, fungal infections--and especially phaeohyphomycosis--are very rare, but appear to be increasing in frequency, especially in the paranasal sinus region.