Mechanical ventilation (MV) is imperative in many forms of acute respiratory failure (ARF). The aim of this work was to review all episodes of MV in a Medical Intensive Care Unit (MICU) during the 11-year period 1976-1986. Four per cent (n = 1008) of 24,899 admissions to the MICU were treated with MV. The mean age of ventilator-treated patients was 53 +/- 18 years, and obviously it increased during the period of study. The average duration of MV was 4.7 d. MICU mortality, hospital mortality and 2-year mortality rates for patients subjected to MV were 33%, 38% and 46%, respectively. The mortality rate did not change during the study period. Cerebrovascular and malignant diseases carried the highest mortality rates, 75 and 79%, respectively, whereas mortality in patients ventilated because of drug overdose (n = 313) was only 2%. The results of this study confirm previously published findings concerning the outcome of MV, and we conclude that the effects of MV remain discouraging in medical and neurological patients. Improved quality of ventilator therapy and monitoring, as well as continued research directed at the causes of ARF, are equally important in reducing the mortality in ARF.