This article focuses on the reactions of farmers subjected to expropriation measures, specifically those for new airport Paris-Nord, in terms of agricultural investments. A discussion of changes in agricultural structure in the region from 1945 to the airport development serves to put the changes since 1965 into perspective. Two types of problems are then discussed : those requiring solution through cooperation within the farming community, and those which concern decisions appropriate to the individual farmer. From questionnaire data, a factor analysis is made of the individual decisions together with certain variables considered important in those decisions. Three factors are retained : one relates the number of potential heirs and the an...