In order to structure their value chains in France and in foreign markets, companies combine two problematics: one pertains to its core business and peripheral activities, the other to the nature of contractual relations and attached risks. These choices will not be made in a similar fashion depending on business sector, the nature of its specific assets or its size. We are developing a theoretical model explaining these choices (meaning "which of the firm’s activities are externalized", and for those which are, to which country and to which commercial partner). We will then compare these explanations with the data contained in the CAM survey.