Recently, the role of various cytokines in the pathogenesis of chronic rhinosinusitis has come under investigation. Various studies have reported increased levels of interleukin-3, interleukin-4, interleukin-5, interleukin-13, and granulocyte macrophage-colony stimulating factor in the sinonasal mucosa of patients with chronic rhinosinusitis. The present study investigated the levels of pro-inflammatory cytokines, including interleukin-1 beta (IL-1 beta), interleukin-5 (IL-5), interleukin-6 (IL-6) interleukin-8 (IL-8), and tumor necrosis factor-alpha (TNF-alpha), in the sinonasal mucosa of patients with chronic rhinosinusitis, and evaluated the response of these cytokines to oral corticosteroids. Chronic rhinosinusitis subjects (n = 15) and control subjects (n = 9) underwent nasal endoscopy and biopsy of the sinonasal mucosa. Chronic rhinosinusitis subjects were subsequently treated with a 10-day tapering dose of prednisone followed by a second sinonasal endoscopic exam and biopsy. Mucosal biopsy specimens were immunostained for IL-1 beta, IL-5, IL-6, IL-8, and TNF-a. In chronic rhinosinusitis subjects, mucosal levels of IL-1 beta, IL-6, IL-8, and TNF-alpha were significantly elevated when compared with control subjects, and levels of IL-5 demonstrated a strong trend toward elevation. In posttreatment chronic rhinosinusitis subjects, levels of IL-6 were significantly decreased when compared with pretreatment levels, and TNF-alpha levels demonstrated a significant trend toward reduction. These findings support the hypothesis that the inflammatory response in chronic rhinosinusitis is associated with elevated levels of pro-inflammatory cytokines, and suggest that oral corticosteroids may exert a beneficial effect by significantly reducing the levels of IL-6 and TNF-alpha.