David Ricardo (1817) provided a mathematical example showing that countries could gain from trade by exploiting innate differences in their ability to make different goods. In the basic Ricardian example, two countries do better by specializing in different goods and exchanging them for each other, even when one country is better at making both. This example typically gets presented in the first or second chapter of a text on international trade, and sometimes appears even in a principles text. But having served its pedagogical purpose, the model is rarely heard from again. The Ricardian model became something like a family heirloom, brought down from the attic to show a new generation of students, and then put back. Nearly two centuries later, however, the Ricardian framework has experienced a revival. Much work in international trade during the last decade has returned to the assumption that countries gain from trade because they have access to different technologies. These technologies may be generally available to producers in a country, as in the Ricardian model of trade, our topic here, or exclusive to individual firms. This line of thought has brought Ricardo's theory of comparative advantage back to center stage. Our goal is to make this new old trade theory accessible and to put it to work on some current issues in the international economy.