Two alternative explanations of interorganizational cooperation are analysed. One is based on an open-systems approach (an outside-in explanation) where cooperation is viewed as a means to manage existing interdependencies with the environment. The other is an inside-out perspective, interpreting cooperation as a means to acquire resources that are necessary in order to establish new interdependencies. The two approaches imply different predictions as to the choice of partners and the type of resources pooled by the partners. This study attempts to reconcile the two explanations, and argues that they are contingent upon the strategic role of cooperation, as expressed by the significant actors of the cooperating organizations.