This paper examines the underwriters' aftermarket activity system in the US.A, in order to recommend the appropriate items for improving the underwriters' aftermarket activity system in the domestic IPO market. First of all, it needs the environment that the underwriter can decide IPO pricing and distribution with the responsibility of its decision. The detailed items for the improvement of the domestic underwriters' aftermarket activity system are as follows; First, it needs an overallotment option and an afteramrket short-covering system for hedging the risk of underwriter's aftermarket activities. Second, it needs the penalty bids system for restricting the flipping of IPOs. Third, the domestic IPO system needs the synchronization of offering date and listing date, and the quiet priod provision.
