Background: World Health Organization considers opioid analgesic use as an important measure in the treatment of pain relief. However, there are limited data about the pattern of opioid analgesic use in tertiary care hospitals in Korea. The aim of this study was to describe the trends in the prescribed amount of the opioid for 13 years from 2000 to 2012 in a single tertiary care hospital. Methods: The data from the prescribed amount of opioid use in patients aged over 18 years were retrieved from medical charts and longitudinal pharmacy records of Seoul National University Hospital. Yearly prescribed amount of opioids were calculated using defined daily dose adjusted by hospital stay (DDD/1000${ullet}$HS). Results: Over the 13 years of the study period, overall use of opioid has increased by 64.1%. Although, the opioid use by hospitalized patients comprised 98%~99% of total amount of opioid use, the proportions of opioid use by outpatient and by cancer patient increased from 1.1% to 2.2% and from 60.5% to 69.3%, respectively. The use of non-injectable opioids has increased by 47% and that of injectables has increased by 70%. While the amount of codeine and morphine use has decreased, the use of both transdermal and injection formulation of fentanyl has increased dramatically. Also, the use of oxycodone has increased, especially in outpatient setting. Conclusion: This longitudinal study showed that opioid analgesic use in tertiary hospital, especially in outpatient is continuously increasing. Improvement in pain management in tertiary care hospital can be cautiously inferred based on this results.