We propose an intelligent clearinghouse system, an electronic marketplace with computer mediated negotiation supports. Most existing electronic market systems support relatively stable markets: Traders are not allowed to revise their bids and offers during the market transaction. The intelligent clearinghouse addresses dynamic markets where buyers and sellers are willing to change their utilities as market conditions evolve. Traders in dynamic markets may suffer a significant loss if they fail to execute transactions promptly. The clearinghouse enables traders to compromise their original utilities to avoid transaction failures. The paper describes the foundation of the clearinghouse system and discusses its trading mechanism, including its order matching method and negotiation support capabilities.