Drug utilization review (DUR) system has been defined as "structured, ongoing initiatives that interpret patterns of drug use in relation to predetermined criteria, and attempt to prevent or minimize inappropriate prescribing." This paper introduces the concept, purpose, and effective application of DUR in Korea. DUR can be classified as retrospective DUR, prospective DUR, and concurrent DUR based on the time direction of applying DUR. DUR can also be classified as quantitative DUR defined by retrospective DUR using databases including previously prescribed medicines, and qualitative DUR defined by DUR reflecting patient's clinical condition. We described the history of developing DUR in the United States and the Europe. Finally current status of DUR in Korea is described and the strategy of future settlement of DUR system in Korea is suggested.