The purpose of this special issue of Economie Rurale is to present a certain number of papers chosen among the contributions to the autumn session 1 981 . This session was organized by the Société Française d'Economie Rurale on the theme «Technical Change and Socio-Economic Dynamics in the Third World Agriculture». The conditions in which the new techniques are usually introduced in the Third World explain to a great extent the difficulties encountered to make them accepted. Generally, the agricultural policy consists in isolated «projects» which are conceived to be export-oriented. Many contributions describe these kinds of situation and stress the frequent opposition between the interests of the State and those of the farmers. The main proposition which many results support is that technical and social changes are impossible to dissociate. Technical change is accepted when it is consistent with the existing system and rejected when it threatens it. Finally, many suggestions were formulated on the way to make observation methods and analyses of farm systems more efficient and better connected with research. The importance of a close relationship between research and higher education in developing countries was also stressed.
