Over the past decade, the increasing power and reliability of microcomputers and the development of sophisticated soft ware designed specifically for use with them has led to significant changes in the way that socioeconomic data are collected and analyzed. The venue of the computations has shifted from off-site main frames, dependent on highly trained operators and significant capital investment in supporting equipment, to desk top and lap top computers, dependent only on the occasional availability of electricity. This means that it is now feasible to quickly transfer new statistical techniques between IFPRI and IFPRI’s collaborators in developing countries, that data manipulation costs of policy analysis have been substantially reduced, and that a new level of complexity and accuracy is now possible in the collection and analysis of survey data in developing countries. As with any new technology, how ever, there are substantial costs in time and money involved in learning the most efficient ways of using this new technology and then transmitting these lessons to others. This series, Microcomputers in Policy Research, represents IFPRI’s collective ongoing experience in adapting microcomputer technology for use in food policy analysis in developing countries. The papers in the series are primarily for the purpose of sharing these lessons with potential users in developing countries, although persons and institutions in developed countries may also find them useful. The series is designed to provide hands- on methods for resolving statistical and data collection problems encountered in food policy research. In our opinion, examples provide the best and clearest form of instruction; therefore, examples—including actual software codes wherever relevant—are used extensively through out this series. This third book in the series, Classification and Regression Trees, CART ™ : A User Manual for Identifying Indicators of Vulnerability to Famine and Chronic Food Insecurity, by Yisehac Yohannes and Patrick Webb, is a manual out lining how to use CART soft ware to conduct classification- and regression- tree analysis. The manual is based on IFPRI’s experiences from its famine research program, which was completed in 1998 with the publication of the book by Joachim von Braun, Tesfaye Teklu, and Patrick Webb, Famine in Africa: Causes, Responses, and Prevention. The manual shows how to use CART to identify indicators of a number of outcomes, including food insecurity and vulnerability to famine. Examples are provided throughout using programs from CART.™