The Intensive Care Unit(ICU) of Severance Hospital was opened on October 18, 1968 with 7 beds and expanded to 19 beds on February 2, 1981. Statistical analysis of ICU patients has already been reported twice: 1. from 1970 to 1977 with 3, 072 cases and 2. from 197S to 1981 with 4,348 cases The following is a clinical analysis of l,458 ventilator cases which comprise6 33.5% of the ICU patients from March 1975 to February 1982. Until 1979 pressure and volume cycled ventilators were use6 at an equal ratio; however, since 1980, volume-cycled ventilators such as the Bennett MA I and MA g and the Bourns LS 104-150 were mainly used. The ventilator cases from the Department of Internal Medicine and Cardiac Surgery rem-ained almost constant at a 30: 30 ratio from 1975 to 1977 However since 1978, the cardiac surgery ventilator cases increased to over 50% of the total. The number of ventilator cases below the ten yearold age group was 396 cases, about 27% of the total. They have increased year by year. Among 587 ventilator cases in 1981, the Bennett MA I and II were used, in 225 and 203 cases respectively. In the under 1 year old age group, 36 cases(43, 9%) were Put on with the Bourns LS 104- 150 and 30 cases(36.6%) on the Drager Babylog I respectively. 487(90.7%) cases were supp-orted with controlled mechanical ventilation(CMV) mode and 135(25%) with the positive end expiratory pressure (PEEP). Of 537 cases, 441(85%) was disconnected from the ventilator within 3 days. Death according to duration of ventilator support was 47(18. 8%), 38(23. 8%) and 14(36.9%) in 1, 2 and 10 days respecitively. But, for the period of 10-19 days, the number of deaths was 4(36.4%) and for 2p or more days 1 case(25%). Reosons for ventilator support were postcardiac operation (301cases, 56%) followed by CNS(central nervous system), IRDS(idiopathic respiratory distress syndrome), and lap- arotomy cases in that order. All ventilator cases with neuromascular disease survived bat none with DEC(Disseminated microvascular cosgulopathy) did. From the above results it can be concluded that ventilator support cases are increasing and the attendant mortality rate is decreasing year by year.