Web services (WS) have become the industry standard tools for communication between applications running on different platforms, and built using different programming languages. The benefits, including the simplicity of use, that Web services provide to developers and users have ensured integration of Web services architecture by almost all IT vendors in their applications. As expected, with the proliferation of mobile phones, PDAs and other wireless devices, the same requirements of making applications talk across platforms has become necessary on mobile devices. This has lead to the mobile Web services (MWS), which are based on the Web services and related technologies like XML, SOAP and WSDL, and which provide the best choice to be used in the architecture for integration of Web services in mobile devices. This chapter discusses WS and MWS in the context of integration architecture, together with their advantages and disadvantages in usage. Since MWS is deployed using wireless technologies and protocols, they are also presented and explained in this chapter.