A clinical study was performed of the respiratory care of 1309 critically ill patients who had been admitted to respiratory intensive care units (RICU) in 1986 and 1987. 1) The number of patients who needed respiratory care was 691 and the mortality in RICU was 1.45% (10 case) in 1986, and 618 and 2.59% (16 cases) in 1987, respectively. 2) The average duration of ventilatory support was 2.1 days in 1986, and 1.9 days in 1987. The patients of thoracic surgery needed respiratory support for 2.6 days in 1986, and 2.3 days in 1987. 3) The mortalities according to department were:1.42% (6 of 424 cases) in thoracic surgery, 1.89% (2 of 107 cases) in general surgery, 20% (1 of 5 cases) in pediatry surgery, and 7.14% (1 of 14 cases) in gynecology in 1986. In 1987, 2.56% (8 of 312 cases) in thoracic surgery, 4.0% (6 of 150 cases) in neurosurgery, 0.96% (1 of 104 cases) in general surgery, and 7.69% (1 of 13 cases) in urology. 4) The most frequently used ventilator was Bear II, followed by Benett MA-I. 5) The major causes of death in RICU were low cardiac output syndrome, sepsis, respiratory failure, and brain damage.