Mycotoxins are toxic secondary metabolites produced by a variety of fungi including Aspergillus, Alternaria, and Penicillium species. The presence of mycotoxins in sinonasal tissue and secretions and any possible link to chronic rhinosinusitis (CRS) or other diseases of the head and neck have not been reported. The authors performed an exploratory study to determine the presence and levels of mycotoxins in the sinonasal tissue and secretions of 18 subjects undergoing endoscopic sinus surgery for CRS. Using commercial enzyme-linked immunosorbent assay kits, samples were analyzed for the following mycotoxins: aflatoxin, deoxynivalenol, zearalenone, ochratoxin, and fumonisin. All specimens were negative for aflatoxin, deoxynivalenol, zearalenone, and fumonisin. Four (22%) of 18 specimens were positive for ochratoxin. The clinical significance of this finding remains to be determined.