Experience with prolonged mechanical ventilation has improved over recent years. Retrospective analysis of the records of 104 patients older than 16 years of age who were mechanically ventilated for more than 29 days over a 29-month period from May 1986 to October 1988 revealed the following findings. The mean patient age was 66.3 +/- 15.7 years (SD). The mean number of in-hospital ventilator days was 59.9 +/- 36.7 days (range, 29 to 247 days). The mean number of days of oral or nasal endotracheal intubation prior to tracheostomy (96 patients) was 21.5 +/- 14.2 days. The mean length of hospital stay for the 104 patients was 79.9 +/- 45.4 days. The majority of the 104 patients (82.6 percent) were surgical patients. Nine patients left the hospital receiving extended mechanical ventilation. Mortality was highest in multiple organ system failure and lowest among the trauma patients. The total days of mechanical ventilation did not appear to be related to mortality if patients older than 16 years survived for seven days. Postdischarge survival of the 53 of 60 patients who survived and whom we were able to contact was 67 percent at one year and 56 percent at three years.