['To investigate the prevalence of Helicobacter pylori (HP) in the nasal cavity of patients with chronic rhinosinusitis (CRS) and to correlate it with the severity of CRS.', 'Intranasal HP was investigated using rapid urease (CLO) testing and immunohistochemical (IHC) analysis and confirmed with transmission electron microscopy. To evaluate the severity of sinusitis, CT scans were graded according to the Lund-MacKay scoring system, and CRS symptom scores were recorded.', 'Twelve of 48 patients (25.0%) were positive, but only 1 of 29 (3.4%) controls was positive for both CLO testing and IHC analysis (P = 0.025). The mean preoperative CT grade (P = 0.439) and symptom scores (P = 0.515) were not related to the severity of CRS.'] Does intranasal Helicobacter pylori colonization correlate with the severity of chronic rhinosinusitis?