This textbook addresses the main economic principles required by agricultural economists involved in rural development. The principles of 'micro-economics' or 'price-theory' are of relevance to economists everywhere, but this book reinforces the message of their relevance for rural development by explaining the theory in the specific context of the agricultural and food sectors of developing countries. Hypothetical and actual empirical illustrations drawn almost exclusively from such countries distinguish this book from other economic principles texts that draw their examples almost invariably from industrialised countries, and also from books more oriented to the issue of rural development. The first half of the book deals with the underlying principles of production, supply and demand. These are essential tools for the study and management of the agricultural sector and food markets. In the second half, supply and demand are bought together into a chapter of equilibrium and exchange. This is followed by chapters on trade and the theory of economic welfare. In the final chapter it is shown that much of the material in the earlier chapters can be combined by agricultural economists into a system for analysing and comparing the effects of alternative agricultural policies. The ability of agricultural economics to provide a consistent framework for the analysis of policy problems thus enables it to make a key contribution to rural development.