The Korean Decimal Classification (KDC) is a national standard classification system of the Korean library community published and maintained by the Classification Committee of the Korean Library Association. This article examines its general history from its advent to the latest edition (KDC 6), its usage, external characteristics including format and layout, internal principles and characteristics including outline and classificatory principles applied, general aspects of the schedule and the major tables, development and maintenance, and general evaluation. It concludes with some ideas and recommendations for future research and development.