Service-oriented architecture (SOA) will form the basis of future information systems. Web services are a promising way to implement SOA enabling the loose coupling of functionality at service interfaces. The focus in SOA changes from traditional software systems to reusable, business-relevant services. Considering the cross-cutting concern of identity management (IdM), it is still an open issue how to construct an SOA-aware IdM architecture enabling “identity as a service” and how to loosely couple the IdM services with SOA’s core concern part. In this paper we present a blueprint for a serviceoriented identity management architecture featuring interoperability by applying existing standards. Our solution has been tested and evaluated in an implementation case study.