BACKGROUND: One nostril must be selected for nasotracheal intubation. In some cases, structural anomalies within the nasal cavity hinder the insertion of the tube or complications, such as epistaxis, develop. This study examined the possibility of using radiography to select the nostril that would induce fewer complications. METHODS: Four hundred and five patients who underwent nasotracheal intubation under general anesthesia were studied. A 7.0-mm internal diameter nasal right angle endotracheal (RAE) tube and 6.5-mm internal diameter nasal RAE tube were inserted into men and women, respectively. Complications were considered to have developed in cases in which insertion of the tube into the nasal cavity failed or epistaxis occurred. The tube was inserted into the other nostril for insertion failures and hemostasis was performed in cases of epistaxis. The degree of nasal septal deviation was determined from posteroanterior skull radiographs or panoramic radiographs; the incidence of complications was compared depending on the direction of the septal deviation and the intubated nostril. RESULTS: The radiographs of 390 patients were readable; 94 had nasal septum deviation. The incidence of complications for cases without nasal septum deviation was 16.9%, that for cases in which the tube was inserted into the nostril on the opposite side of the deviation was 18.5%, and that for cases in which the tube was inserted into the nostril with the deviation was 35.0%, showing a high incidence of complications when intubation is performed through the nostril with septum deviation (chi-square test, P < 0.05 ). CONCLUSIONS: Although there were no differences in the incidence rates of complications between intubation through the left nostril and that through the right nostril, radiological findings indicated that incidence of complications significantly increased when the tube was inserted into the nostril with the septum deviation.