A prospective study of the complications and consequences of translaryngeal endotracheal intubation and tracheotomy was conducted on 150 critically ill adult patients. Adverse consequences occurred in 62 percent of all endotracheal intubations and in 66 percent of all tracheotomies during placement and use of the artificial airways. The most frequent problems during endotracheal intubation were excessive cuff pressure requirements (19 percent), self-extubation (13 percent) and inability to seal the airway (11 percent). Patient discomfort and difficulty in suctioning tracheobronchial secretions were very uncommon. Problems with tracheotomy included stomal infection (36 percent), stomal hemorrhage (36 percent), excessive cuff pressure requirements (23 percent) and subcutaneous emphysema or pneumomediastinum (13 percent). Complications of tracheotomy were judged to be more severe than those of endotracheal intubation. Follow-up studies of survivors revealed a high prevalence of tracheal stenosis after tracheotomy (65 percent) and significantly less after endotracheal intubation (19 percent)(p < 0.01). Thirty-nine of 41 (95 percent) patients with endotracheal intubation and 20 of 22 (91 percent) patients with tracheotomy had laryngotracheal injury at autopsy. Ulcers on the posterior aspect of the true vocal cords were found at autopsy in 51 percent of the patients who died after endotracheal intubation. There was no significant relationship between the duration of endotracheal intubation or tracheotomy and the over-all amount of laryngotracheal injury at autopsy, although patients with prolonged endotracheal intubation followed by tracheotomy had more laryngeal injury at autopsy (P = 0.06) and more frequent tracheal stenosis (P = 0.05) than patients with short-term endotracheal intubation followed by tracheotomy. Adverse effects of both endotracheal intubation and tracheotomy are common. The value of tracheotomy when an artificial airway is required for periods as long as three weeks is not supported by data obtained in this study.