For the purpose of selecting the media for an advertising campaign designed to reach consumers, advertising men in France have hitherto had at their disposal information coming from two types of source wholly independent the one from the other : 1. Panels or sample surveys supply them with information on the socio-demographic characteristics of the consumers who constitute the advertising target ; 2. Research by the C.E.S.P., the O.J.D. and surveys carried out by some of the media themselves, giving information on the audience they serve and on the characteristics of this audience. To bring together these two groups of information it was necessary to make use of complex models involving probability techniques, and for a longtime the researchers' efforts were concentrated on the elaboration and perfecting of these models.