['It has been postulated that fungal organisms might represent the immunologic target initiating and maintaining the disease process in patients with chronic rhinosinusitis (CRS). The presence of fungi in nasal mucus has been established by different groups, but so far it has not been shown how the immune system could even recognize such extramucosal--extracorporal--fungal targets. The aim of this study was to determine whether fungal DNA is present in tissue specimens taken from patients with polypoid CRS.', 'Twenty-seven surgical specimens were collected from patients suffering from CRS. Fifteen surgical specimens from healthy ethmoidal mucosa served as controls. A second set of controls consisted of five surgical specimens of acoustic neuroma, which were included to rule out contamination within the protocol. All paranasal tissue samples were treated and rinsed carefully with a solution of Dithiothreitol to digest any nasal mucus and ensure that only tissue was examined. A highly sensitive two-step polymerase chain reaction (PCR) was applied to detect fungal DNA, using one universal primer for unspecific detection of fungal DNA and a second primer pair specific for Alternaria.', 'Fungal DNA was detected in all 27 CRS specimens equally with both PCR primers. Controls from healthy paranasal mucosa were positive using the panfungal primers in 10 of 15 cases but were all negative for Alternaria DNA. PCR was negative for fungal DNA in all five neuroma specimens.'] Is fungal DNA present in tissue specimens of patients with chronic rhinosinusitis?