To be held in conjunction with: INTEROP-ESA 2005 (http://interop-esa05.unige.ch/).Service-oriented architectures and enterprise application integration using Web Services, both in the public sector and in industry, are emerging. This technology affects the way organisations plan and utilise resources both in a short-term and a long-term sense. Web Services allow organisations to, for example, offer legacy system functionality and access to legacy systems in a new way, and to become more flexible to customer and partner needs. There is hence a great strategic perspective to be placed on Web Services. Currently, the wide deployment of eService-oriented technology is constrained by the heterogeneity in the existing types of eServices (e.g. web services, peer-to-peer services, grid services) and in the related protocols and standards. This heterogeneity is a major obstacle for the reuse of existing eServices and for their interoperability. This workshop attempts to gather researchers and practitioners in order to explore various aspects of Web Services, covering both a technical and a business perspective.