Objectives/Hypothesis The role of respiratory viral infection in the pathogenesis of chronic rhinosinusitis (CRS) has been rarely studied and remains controversial. The aim of this study was to explore the prevalence of respiratory viruses in the chronic status of CRS. Study Design A case-control prospective study. Methods Fifty-three control subjects, and 67 CRS with nasal polyp (CRSwNP) and 61 CRS without nasal polyp (CRSsNP) patients without signs of acute viral infection were enrolled. Epithelial cells scraped from the middle nasal meatus were tested for the nucleic acid of nine common respiratory viruses using polymerase chain reaction assay. The clinical disease severity was compared between subjects with and without viral infection. Results The overall detection rate of viral infection was 75.47%, 68.66%, and 73.77% in controls, CRSwNP, and CRSsNP, respectively, and no significant difference among studied groups was observed. There was no significant difference in detection rate of any specific individual virus or multiple viruses among the groups studied either. Visual analog scale scores of symptoms, computed tomography scores, or endoscope scores did not show obvious difference between subjects with and without viral infection. Conclusions Although a high frequency of viral infection could be observed in the middle nasal meatus, no increase of frequency of viral infection could be demonstrated in chronic persistent phase of CRSsNP and CRSwNP. The contribution of the interaction between viral infection and host immunity to the pathogenesis of CRS remains to be determined. Level of Evidence 3b. Laryngoscope, 124:832-837, 2014