The first edition of this book appeared in 1985. In grew out of an earlier book, International Economics, which was widely used but was sometimes criticized as being too difficult for elementary courses and too brief for intermediate courses. When I began to write this book, I planned to fill gaps in the earlier one but to keep it shorter than most other textbooks. Each chapter turned into three, however, as I filled more gaps and carried the analysis further.

The second edition of this book appeared in 1989 and differed greatly from the first. In the first edition, for example, two trade models featuring factor substitution appeared in a single chapter, and the analysis of trade and growth appeared in another chapter. In the second edition, each model appeared in a separate chapter, along with the analysis of trade and growth in the context of that model. Furthermore, I added a chapter on trade and trade policy under imperfect competition.

The third edition made several more changes, which were well recieved and are retained in this edition:

• The theory of trade policy is integrated with pure trade theory. The analysis of tariffs begins in Chapter 2, right after the analysis of the gains from trade, and the effects of tariffs are examined again in the context of models developed in subsequent chapters. The results are then summarized in Chapter 9, which examines the instruments and uses of trade policy.

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