SOA and web services are supposed to increase integration capabilities, stimulate interorganizational processes, and thereby improve coordination in distributed business networks. They also foster the idea of dynamic business networks with quick connect and disconnect relationships. While service-oriented architecture (SOA) concepts are increasingly adopted in practice, they are still mostly applied within company boundaries. Little research has systematically analyzed how SOA is implemented in inter-organizational relationships and business networks. In addition, SOA concepts are not yet sufficiently linked to the mature stream of research on inter-organizational information systems (IOS). Hence, authors lack a more fundamental understanding of how SOA is used within business networks. This research aims at filling this gap. First, authors propose a multi-dimensional classification scheme for assessing SOA adoption in business networks. This scheme is derived from inter-organizational systems (IOS), SOA and business networking literature. Second, they analyze inter-organizational SOA cases to identify focus areas and patterns of SOA adoption in business networks. Third, authors compare their findings to the propositions from IOS and SOA literature.