Intellectual Property laws create exclusive rights to inventions, to expressive works, and to valuable "know how," and do so in an effort to induce inventors, writers, musicians, photographers, and so forth, to create and market their works. But, sometimes, holders of IP behave in anticompetitive ways, and use their IP to effectuate anticompetitive plans. When this happens, the Federal Trade Commission and the Department of Justice invoke antitrust laws to curb the anticompetitive behavior. Courts and commentators often disagree about which IP behavior comprises antitrust violations. We will survey some of the most common situations, including "pay for delay," patent pools, standard setting, division of markets, and price fixing.