With the emergence of Web Services into the mainstream the developer has to learn how to architect and build service-oriented systems. While service-orientation isn’t a new concept, the rapid convergence of the industry on Web Services technology has brought the concept of Ser-vice Oriented Architectures (SOA) to the forefront of many developers’ minds. Over the last decade we learned how to construct software systems using patterns that adhered to the concepts of Object-Orientation. Now, Service-Orientation requires us to adapt to a new approach to system integration and application development. However, at the moment most of us are still learning about this new technology and so we tend to apply familiar patterns when building Web Services-based applications. Applying object-oriented patterns to service-based systems is generally a poor idea since the scale of a typical Object-Oriented application (generally within a single enterprise or depart-ment) is dwarfed by the scale of a Web Services-based application (which may span many en-terprises and departments). It is crucial to remember that the use of SOAP and WSDL in our ap-plications does not constitute service-orientation. This article outlines the basics of (Web) Service Oriented Architectures and draws out the dis-tinguishing features of SOA that make it the right approach to take when developing Web Ser-vices-based applications.