The concept of intensive care has developed from experience in recovery rooms, in anesthetic work, and in early specialized units in different fields of medicine. Between the First and the Second World Wars special units were created in some German hospitals. Intensive care often means a combination of recovery-room service and intensive therapy. Intensive care, especially respiratory care is an important part of the responsibility of the anesthesiologist. So, we have analyzed statistically 3, 072 I.C.U. patients who were admitted during a period of 7 years beginning October 18, 1968 when the I.C.U. at Severance Hospital was opened, The results are as follows: I. Cases admitted to the I.C.U. (March,1970-August, 1975 ) 1) For 5 and a half years, the total number of patients was 2, 479. These patients were 2.7% of 91,400 patients who were admitted into Severance Hospital. 2) The mortality rate was 20.0% . Mortality rate was highest in 1970 (23. 7%) and lowest in 1975 (13. 5%). It has gradually decreased every year. 3) Total occupied bed days were 9,840 days (average 4,0 days). The occupied bed days of the majority of the patients (83.6%) were below 5 days comprising 88.3% of the total expired patients. 4) 50% of the patients were in the 21 to 50 year age group. The highest mortality rate occurred in the 51 to 60 age group (24.3%). 5) The number of patients admitted in the department of internal medicine was 702 cases (28.3%) which was the highest among all departments. The mortality rates of the departments of pediatric and neurosurgery were 40. 3% and 34. 7% respectively and those were relatively high values. 6) All I.C.U. patients have been divided into two categories, operative and non-operative. The operative cases were 1, 264 (51. 0%) and non-operative 1, 215 (49. 0%,). The mortality ,The Journal of The Korean Society of Anesthesiologists VoI. 9, No. 2, 1976 rate of the non-operative cases (22. 5%) was higher than operative (17. 6%). 73 Cardiovascular disease was the commonest cause of death of I.C.U, patients (107 cases) admitted from March, 1974 to August, 1975 (30 cases, 28. 0%). Respiratory support cases (October 18, 1968-August 31, 1975) ;. During the 7 year period, of all I.C.U. admission cases (3,072) 423 cases (13.8%) received respiratory support. These patients gradually increased every year. 2) The mortality rate was 44. 0% which was more than twice the over-all mortality rate of. I.C.U. admission patients. 3) The mortality rate was highest in the 21 30 age group (18. 7%). 4) The department of internal medicine admitted the largest number of cases (153 cases, 36. 2%). 5) Of all conditions, cardiovascular disease was most frequent (126 cases, 29. 8%). Here we have discussed the definition of I.C.U., the responsibility and important role of the anesthesiologist in the I.C.U. by illustrating present situations and presenting problems at the I.C.U. in Severance Hospital.