Background : Recently marketed Cyclooxygenase 2(COX-2) selective inhibitors promoted as safer nonsteroidal anti-inflammatory drugs(NSAIDs) regarding gastric toxicity. Korea National Health Insurance Review Agency(HIRA) revised claims review criteria of COX -2 selective inhibitors in June 2001 and October 2001. This study was performed to assess the prescribing pattern of COX-2 selective inhibitors across the change in claims review criteria. Methods : This study was a retrospective drug utilization review study from August 1, 2000 through March 31, 2002. Data on drug prescriptions were obtained from the Health Insurance Claims Database which included the whole outpatient clinics prescription data in Busan metropolitan city, Korea. Demographic information such as age, sex and prescription information including brand name, prescription date, daily dose, duration and diagnosis were collected. COX -2 selective inhibitor prescriptions were screened and analyzed by the age, sex, and type of hospitals using SAS Windows ver. 8.1. Results : Total COX -2 selective inhibitor prescription frequency was 115,473 during this period. Among total prescriptions 69.2% was prescribed at primary ambulatory units and 79.1% was used for female patients. The prescription frequency of COX-2 selective inhibitor was significantly decreased from June 2001 to October 2001 (p<0.001). Conclusion : COX -2 selective inhibitors prescription frequency shows sharp decline by change of claims review criteria. This result implies administrative policy such as claims review criteria can substantially influence drug prescription patterns, specially which has its alternatives.