With the growing adoption of service oriented computing, web services are becoming important building blocks of distributed applications. As these services inevitably evolve and change, service version management will increasingly become a key part of the service lifecycle. To address this versioning requirement from the service provider?s point of view, we propose two key concepts. The first is to draw a distinction between a service?s interface version and its implementation version. The second is to employ a tiered hosting model which echoes this structure, by introducing a version routing point in front of the actual service implementation versions. This version routing point routes versioned requests to the appropriate implementation versions. We have implemented a prototype of our approach on IBM?s WebSphere Process Server and WebSphere Enterprise Service Bus. We show our results with a versioned test service to demonstrate the capabilities of our proposal.