The authors explore questions related to the presence of middlemen in electronic markets. How does the existence of intermediaries affect the efficiency of electronic markets? What is the role played by various strategies that these intermediaries might adopt? What if they can pursue more sophisticated pricing strategies? The authors developed a simulation of an electronic marketplace, specifically a marketplace of information. All roles in these simulations were played by automated agents, which were designed to act as information producers, information suppliers, or information "middlemen" (called InfoCenters). Simulations were then run to test how these InfoCenter intermediaries affected the market's efficiency and price behavior. The authors looked at several different strategies for these middle-agents, comparing how they-and the market-did in each case. It turned out that InfoCenters could significantly enhance the efficiency of information marketplaces, and sophisticated InfoCenters did the best of all.