Nosocomial maxillary sinusitis during mechanical ventilation may cause life-threatening complications in ICU patients. The aim of this prospective study was to compare the incidence of maxillary sinusitis according to the route of intubation. 111 consecutive adult patients (mean age: 53, mean SAPS: 12) were randomly assigned to receive either orotracheal (n = 53) or nasotracheal (n = 58) intubation. All had a nasogastric feeding tube. Patients with head trauma or mechanical ventilation for less than 48 h were excluded. Sinusitis diagnosis was made by radiography (waters' view) at the bedside. The two groups were similar in age, SAPS, duration of ventilation. Maxillary sinusitis occurred in 1/53 (1.8%) of the orotracheal group (on the nasogastric tube side), and in 25/58 (43.1%) of the nasotracheal group (7 on the nasogastric tube side, 11 on the endotracheal tube side, 7 bilateral; p less than 0.001). Nine of the 26 cases of sinusitis were initially treated by sinus drainage because of signs of infection (3 failures) and the 17 others were treated by tube removal. This procedure proved successful in 12 out of 17 cases but secondary drainage was performed in 5 cases (1 failure). Incidents related to the route for long-term intubation were significantly (p less than 0.001) more frequent in the orotracheal group (8/53 vs 2/58), however no patient died because of them. In this study, long-term orotracheal intubation reduced significantly the incidence of maxillary sinusitis in comparison with nasotracheal intubation.