The online world has developed from a source of information to a complex economic and social environment. However, many online environments fail to function eciently due to the lack of reliable reputation and anonymity of users. We propose a tradable reputation mechanism and conduct a virtual eld experiment, using Second Life as an experimental platform, to investigate the role of reputation trading, based on our game theory analysis of the economic in uence of tradable reputation. We introduce an avatar market that allows users to buy and sell avatars in terms of the reputation. Our main theoretical results show that reliable reputation is induced in a separating equilibrium where users are separated based on their ability in ful lling tasks or transactions. We generate ve hypotheses to test in the eld experiment. We also describe a computer system that realizes the proposed mechanism as a basis for the eld experiment.