Although companies are more and more developing complex networks of connections with their partners and customers and shifting their focus towards expanding the knowledge management concept externally, research addressing the management of knowledge across organizational borders is rather sparse. Our aim in the present paper is to develop a typology of cross-organizational networks of information and knowledge flows. In order to arrive at such a typology we examine two issues. The first concerns the locus of control on the processes that enable knowledge flow. The second refers to the tradability of the streams of knowledge that flow among organizational entities. We examine four types of knowledge networks: open knowledge networks, private knowledge networks, closed knowledge exchanges and knowledge markets. For each type of knowledge network, we examine its distinct characteristics, study related examples, consider the associated research challenges and analyse an indicative case.