UDDI is a standard registry for Web services, but so far its search functionality has been limited to keyword search. These authors propose a UDDI enhancement called Matchmaker, which supports semantic service capability discovery. Since September 2003, they have deployed Matchmaker in one of four official UDDI registries operated by NTT-Communications. In this article, they introduce Matchmaker and illustrate client tools that lower the threshold for using semantics in service discovery. Experiments show that Matchmaker search consumes about 5 seconds more time than a typical keyword-based search. The authors also collected user information through questionnaires and by observation of search behavior.