When can producers cooperate, and when must they compete? Is the NFL—or NCAA—a beneficial collaboration, a consumer-harming cartel, or a hybrid of both? Antitrust law, born in the shadow of the Second Industrial Revolution’s titanic steel and oil companies, provides answers to questions such as these. The course explores the evolution of this common-law-like statutory regime, in which courts strike a dynamic balance among disparate policies, including consumer protection, allocative efficiency, and the innovation-spurring rewards of monopoly. Using major cases and enforcement-agency pronouncements, we make reasoned assessments of the probable legality of assorted business practices in varied sectors, from sports leagues to software firms, and from mining to medical care. A few basics of economic reasoning routinely appear in the cases and commentaries, so we devote some attention to them; but have no fear, it’s straightforward stuff.