For some time it has been common knowledge that it is in traditional agriculture that most of the world's agricultural producers are engaged. It has also been known since FAO began publishing its annual reports on the world agricultural situation, if not before, that the rate of progress of agriculture in the advanced countries of the world differs from that in the less-developed countries. In the advanced countries, where agriculture is a minor industry in terms of the number of people engaged or in its contribution to the GNP, it has been making progress and has been producing more per person or per unit of land. In the less-developed countries, where it is a major industry, it has been registering little, if any, advance. People with experience in less-developed countries know that such increase as there has been has occurred principally in the more or less commercialized large-farm sector; and that the traditional sector, composed chiefly of small farms, has had little share in it. Considering all this, and the fact that the development of the poor countries has become of international concern, it is rather surprising that so many years have had to pass before a leading agricultural economist published a book dealing with one of the major problems of these countries: the transformation of traditional agriculture.