A prohibition of unfair supporting practices by Subparagraph (7), Paragraph (1),Article 23 of The Monopoly Regulations and Fair Trade Act, which is defined as assisting practices of a specially related person or other corporations through the provision of excessive economic benefit by providing or transacting them with funds, assets, goods and mans, can be implemented effectively, only if its criteria are set with high clarity and rationality.Furthermore, the regulated subjects are to be confined teleologically, i.e. with regard to control of excessive general concentration of economic power in Korea. In this respect, the prohibition of such unfair supporting practices should be reduced to transactions between affiliated companies and specially related persons of a large corporate group.Supporting practices occurred in a large corporate group, in other words internal trade, may have positive effects like reduction of transaction costs and not always threaten fair trade order. As refusal to deal or discrimination is left in principle to a free decision of an undertaking, trade practices which support other companies controlled by the same corporate group should be deemed illegal, only if it hamper competition in the market where the supported company is active or it is likely to create or strengthen general concentration of economic power.The problem raised in the implementing process of that prohibiton lies especially in that the criterion of economic concentration seems so vague and far from being legal assessment. Rather it is a policy objective, which is in its nature inappropriate for being incorporated to normative decision process. The unfair supporting practices should be therefore de lege lata understood just as an extension of unfair trade practices. For an effective prohibition of supportingpractices by large volumes which tend to strengthen general concentration by large corporate groups, an introduction of ex ante regulation should be de lege ferenda. considered.