Major purposes of this study were to investigate the administration patterns of analgesics and sedatives in SICU and to identify the factors influencing the use of prn analgesics and sedatives by ICU nurses. The sample of this descriptive study was 50 adult patients in SICU and 53 ICU nurses. Patient's medical records were reviewed to investigate names, doses, the routes of administration, the interval of administration, and the type of prescription of sedatives and analgesics administered. Study medications were narcotics, hypnotics, and antipsychotics. To identify the factors influencing the use of prn analgesics and sedatives, 53 ICU nurses checked 9 items, and rank them from first to fifth. The selection of items was based on the previous studies and the experience of the investigator. The results of the study are as follows: 1. The mean age of the subjects was 53 years, 24 patients out of 50 subjects had received mechanical ventilation therapy. Most of the patients received neurosurgeries and abdominal surgeries. 2. For 4 days, 13 total study medications and combination of these were administered to the patients. Commonly prescribed drugs were Ketoprofen and Midazolam. Twenty six to fourty two percent of the patients did not receive any drugs for at least one day during the four days. 3. On the average, the study drugs were administerd 1.4 to 2.6 times per day during 4 days. 4. More than 50 percent of the prescription was as-needed (prn) except those of the POD 3. Fourteen percent of the patients did not have any prescription for sedation and pain control after surgery. 5. Examination of the frequency of sedatives and analgesics bolus administration revealed that a greater number of doses were given during daytime (from 7 am. to 7 pm.) than nighttime (from 7 pm. to 7 am.). The difference was significant at Alpha, .05. 6. First factor that most influenced nurses to administer sedatives and analgesics for intubated patients was the evaluation of patient's vital signs (51%). For non- intubated patients, the factors that nurses considered important were the patients' complaints of pain (64%) and evaluations of patients' vital signs (23%). In conclusion, the results of this study indicate that patients in SICU might not receive enough analgesics and sedatives to feel completely free from pain during the post operational period. Future study should be focused on the evaluation of the adequacy of current practice for pain and anxiety control in terms of the SICU patient's response.