Service-Oriented Architecture (SOA) is a viable option for systems development, systems integration, and leverage of legacy systems. Despite its positive contributions and potential, SOA has been subjected to significant hype and inflated expectations, and past research efforts in this area have been unfocused. As a result, there is a strong need for systematic and unbiased research. Based on a synthesis of two leading efforts, this chapter presents a framework of research challenges for service orientation and focuses on the topics related to the migration and evolution of service-oriented systems. The chapter reviews current progress as well as gaps in addressing challenges that are derived from the framework.