We study several problems related to game theory. These problems are motivated by e-commerce applications and applications of game theory to computer system and network design. In mechanism design, we aim to develop mechanisms with useful properties which optimize an objective function, such as seller’s revenue or global welfare of the system, in the worst- or average-case. Our work shows that techniques from learning, on-line algorithms, and coding theory can be applied to mechanism design. We also study complexity of computational problems that come up in implementations of game-theoretic mechanisms. Finally, we are interested in research problems on the borderline of Economics and Computer Science, including Game Theory, Social Networks, and Electronic Markets.