Business Interest Associations vary widely in their governability defined as their ability to unify members interests and ensure goal compliance. How can these variations be explained? To what extent is associational effectiveness governed by factors in the external environment of an association and of its members, and to what extent can improvement programmes undertaken by associations themselves make a difference? Drawing upon interviews undertaken with 50 EU business associations in the autumn of 1998 and ongoing subsequent member interviews, analysis enables researchers to ascertain the conditions under which associations are likely to be in a position to contribute to the process of European integration. Comprehensive directory research is also used to settle a long-standing dispute about the number of Euro groups .