Those who used the first or second edition will notice changes. For on thing, there are more chapters. The division of chapters into small, distinct sections has always made this book more flexible than others; now this flexibility is further enhanced by the new and more flexible detailed organization of chapters. The new chapter organization increases emphasis on scale economics and imperfect competition as distinct causes of trade. The first edition of this book pioneered the inclusion of these topics in an undergraduate text, and this third edition continues to provide the most thorough treatment available of the newer theories of international trade. The "Case Studies" that earlier users liked so much are still here, joined by many new ones. The majority of sections are followed by a selection of problems. A Study Guide is available, which contains the answers to nearly all of these problems as well as additional problems, self-tests, detailed review of basic ideas, and review questions for every chapter in this text.