This article discusses the key issues in the regulation of business combinations in Korea by analyzing the more important among the recent decisions of the Korea Fair Trade Commission (“KFTC”) involving business combinations. First, it discusses the formation of control relationship among the participants in a given business combination, with reference to the Merger Review Guidelines of the KFTC. Second, it discusses the delineation of the relevant market under Korean law. The Merger Review Guidelines specifies three dimensions for delineating a relevant market: (a) product, (b) geographic area and (c) stage of trade and counterparty. The factors considered by the KFTC when delineating a relevant market are presented and compared with the factors considered in foreign jurisdictions. The need for delineations of the relevant markets from a dynamic, rather than static, perspective is explained. Once the relevant market has been delineated, the KFTC evaluates whether the business combination at issue would substantially restrain competition in that relevant market. This article discusses the elements of such evaluation, both uantitative (including the use of market share data, purchase ratio data, CRK and the Herfindahl-Hirschman Index) and qualitative (including the consideration given to availability of imports, ease of market entry, possibility of collusion among competitors, and the market foreclosure effect). Finally, two exceptions to the prohibition against anticompetitive business combinations are discussed: (a) combinations that would bring about an enhancement of efficiency outweighing the anticompetitive effect and (b) combinations involving a failing company (as participant) where there is no less anticompetitive alternative for revitalizing that failing company.