The IEEE International Conference on Web Services (ICWS) has been a prime international forum for both researchers and industry practitioners to exchange the latest fundamental advances in the state of the art and practice of Web-based services, identify emerging research topics, and define the future of Web-based services. All topics regarding Web-based services lifecycle study and management align with the theme of ICWS. In 2013, we will celebrate our 20th version of gathering, to strive to advance the largest international professional forum on Web-based services. The IEEE 2013 World Congress on Services (SERVICES 2013) is the biggest international forum that explores the science and technology of Services Computing, which was formally promoted by IEEE Computer Society since 2003. Under the umbrella of SERVICES 2013, ICWS 2013 will co-locate with the following service-oriented sister conferences: the 6th IEEE 2013 International Conference on Cloud Computing (CLOUD 2013), the 10th IEEE 2013 International Conference on Services Computing (SCC 2013), the 2nd IEEE International Conference on Mobile Services (MS 2013), and the International Congress on Big Data(BigData Congress 2013). The five co-located theme topic conferences will all center around "services," while each focusing on exploring different themes (web-based services, cloud-based services, services innovation lifecycle, mobile services, and Big Data-based services). From technology foundation perspective, Services Computing has become the default discipline in the modern services industry. As a major implementation technology for modernizing services industry, Web services are Internet-based programmable application components published using standard interface description languages and universally available via uniform communication protocols. In its 20th version, the program of ICWS 2013 will continue to feature research papers with a wide range of topics, focusing on various aspects of web-based services. Some of the topics include Web services specifications and enhancements, Web services discovery and integration, Web services QoS (e.g., security, performance, reliability, fault tolerance, etc.), Web services standards and formalizations, Web services modeling, Web services engineering, Web services testing, Web services-based applications and solutions, Web services realizations, semantics in Web services, Web services supporting Cloud Computing, Web services lifecycle management, and all aspects of Service-Oriented Architecture (SOA) infrastructure and middleware. Extended versions of selected research track papers will be invited for potential publication in the IEEE Transactions on Services Computing (TSC), International Journal of Web Services Research (JWSR), and International Journal of Business Process Integration and Management (IJBPIM). Both TSC and JWSR are indexed by SCI and EI [Link]. According to Thomson Scientific, JWSR is listed in the 2008 Journal Citation Report with an Impact Factor of 1.200. The journal ranks #47 of 99 in the Computer Science, Information Systems and ranks #37 of 86 in Computer Science, Software Engineering. ICWS Proceedings are EI indexed.