A total of 434 patients admitted to the intensive care unit for mechanical ventilation were followed prospectively to investigate the influence of a nasotracheal tube on the paranasal sinuses. Twenty‐five patients died before the examination was completed. The rest were examined for clinical symptoms of sinusitis. If sinusitis was suspected or the patients were intubated for 5 days or more, an x‐ray of the sinuses was performed. In patients intubated for less than 5 days (N = 357), sinusitis was clinically suspected in three, but radiograph‐ically verified in only one. In patients intubated for 5 days or more (N = 47), 23 (49%) had affection of the paranasal sinuses. Patients needing a nasotracheal tube should be examined for sinusitis if they are intubated for more than 5 days or if unexplained fever, sepsis or purulent nasal secretion develops. If the suspicion is confirmed, the nasotracheal tube should be re