The authors have developed a natural order for students to understand the antitrust field based upon a division of the practices challenged into two groups. One group of competing firms eliminate competition purely among themselves. The second group of firms seek to exclude actual or potential competitors. In selecting and editing cases, the authors have preserved a sense of the historical development and jurisprudential character of antitrust law. In citing lower-court cases and secondary materials, the authors have selected only material that casts significant illumination on the subject.