Service-oriented architectures (SOAs) aim to improve the ability of organisations to quickly create and reconfigure IT systems to support new and rapidly changing customer services. The key idea is to move away from monolithic systems, towards systems which are designed as a number of interoperable components, for enhanced flexibility and reuse. This paper will describe how semantic descriptions of such services can improve the service discovery and composition processes and move towards an SOA that is more dynamic and scalable. An account of a case study involving BT Wholesale’s B2B gateway is given.