A number of knowledge management (KM) approaches based on individual organizational KM strategies and business requirements have been developed without taking system interoperation into consideration. In this paper, a collaborative inter-organizational KM network is proposed to allow various organizations to access and retrieve inter-organizational knowledge. Ontology and mediation methods are applied to the network to enable heterogeneous knowledge management systems to communicate and collaborate with one another. The retrieved interorganizational knowledge is used to support organizational KM process. While knowledge engineers can reuse the inter-organizational knowledge to create and evaluate its own organizational knowledge, general users benefit from the effectiveness and efficiency of searching for relevant inter-organizational knowledge within the network.