Two decades ago, noticing the increasing attention being given to questions of economic organization and the nature of firms, we compiled the initial version of this Reader. At that time, we noted the growing frequency of references to writings such as Ronald Coase's 1937 classic as well as work published in the 1970s by Armen Alchian and Harold Demsetz, Michael Jensen and William Meckling, and Oliver Williamson. The years that followed have seen those and related works serve as the core of a literature that has deepened in institutional detail, branched out into empirical studies, and inspired progress in formal analysis. Coase's pioneering role was recognized with the awarding of a Nobel Memorial Prize in Economic Science in 1991. Williamson's ideas, which build on those of Coase and incorporate a number of new elements, have occupied a prominent place in the study of organizations by economists and students of related disciplines. What can be called the “new institutional economics” has had increasing influence, as shown by its treatment in a growing formal analytical literature by such writers as Oliver Hart, Bengt Holmstrom, and Paul Milgrom, a marked departure from a time when the “mathematical-formalist” and nonmathematical literatures included few citations by the one of the other. With unfolding research still suggesting that our original selection of “classic writings” indeed brought together core sources, with interest in the materials remaining strong, and with the fruits of more recent research providing the basis for further steps forward, we are pleased to offer our second revision of The Economic Nature of the Firm: A Reader.