We know very little about the history of the Belgian contribution to the European Construction from 1945 to the present. That will say that the historiography has to fill a gap, more particularly in the field of therole of leading men and pressure groups. The case of the European League for Economic Cooperation (ELEC) is a good one because it shows the determinant influence of a man (Paul van Zeeland) and its friends (e.g. Joseph Retinger) over the « attentive opinion», not only in Belgium but also in other European countries, at the beginning of the cold war about the so called European Challenge. But the birth and development of the ELEC show also that national problems could deeply influence an international initiative. The opposition of the Socialists in Belgium considerably hindered the international issue of the ELEC.