Sinusitis is a complication known to accompany nasotracheal intubation, but its frequency has not been well documented. Twelve patients suffering from cerebral haemorrhage or from cranial trauma and treated with mechanical ventilation were examined for radiological and bacteriological signs of sinusitis with CT-scanning, and cultures of nasal pus discharge. All patients showed radiological signs of sinusitis within 3 days after intubation. They all developed fever, six with a known focus outside the sinuses. There was an even distribution of Gram-negative and Gram-positive bacteria. It is concluded that sinusitis should be considered where fever occurs without known focus in patients with nasotracheal intubation.