An important objective of the Semantic Web is to make Electronic Commerce interactions more flexible and automated. To achieve this, standardization of ontologies, message content and message protocols will be necessary. In this paper we investigate how Semantic and Web Services technologies can be used to support service advertisement and discovery in e-commerce. In particular, we describe the design and implementation of a service matchmaking prototype which uses a DAML-S based ontology and a Description Logic reasoner to compare ontology based service descriptions. We also present the results of initial experiments testing the performance of this prototype implementation in a realistic agent based e-commerce scenario. Categories and Subject Descriptors H.3.5 [Online Information Services]: Web-based services; I.2.4 [Knowledge Representation Formalisms and Methods]: Representation languages; D.2.8 [Software Engineering]: Metrics-performance measures. General Terms Languages, Standard...