70 patients (39 men and 31 women) submitted to a prolonged intubation at the Centre respiratoire de la Clinique médicale universitaire de Lausanne have been investigated. They represent the half of the patients having survived of 488 cases treated between January 1966 and June 1974. 33% of the investigated patients (i.e. 18% of all men and 48% of all females) complain about a permanent dysphonia related to the intubation. 17% of the patients (i.e. 13% of all men and 23% of all females) presented with a laryngotracheal lesion induced by the prolonged intubation. This study shows that laryngo-tracheal complications following prolonged intubation are more frequent in females than males. The time of intubation is a determinant factor for the development of complications. Following the first 48 h or intubation of the risk of laryngo-tracheal complication is proportional to the duration of the permanence of the nasal tube. The presence of pathogenous microbes (Klebsiella, Staphylococcus aureus, Bacterium coli, Proteus, Pseudomonas aeruginosa) in the tracheo-bronchial secretion is also important for the development of sequelae. In conclusion, laryngo-tracheal complications following prolonged intubation occur in the male when predisposing factors are present, whereas in the female post-intubation sequelae occur without such predisposing factors.