The only variables which are taken into consideration in both media audience surveys and product market surveys are the socio-economic characteristics of the individuals in question. To define a target population for the purposes of an advertising campaign we have therefore been obliged to use these socio-economic characteristics as relay variables. But these variables have shown themselves to be insufficiently predictive of consumption or ownership of products. Consequently, research workers have turned to surveys in which individuals are questioned at one and the same time on their behaviour with respect to media and their consumption of merchandise; these are called media-product surveys. The ill-considered use of such surveys can lead to disappointing results. We therefore propose a method in which the definition of a target population is seen as a series of reasoned decisions and not as the simple reflection of the present market for a given category of products. The media-product survey retains its utility; it complements major media audience surveys and market surveys, without claiming to replace them.