This chapter presents a context-based approach for personalizing Web services so that user preferences are accommodated during the performance of Web services. Preferences are of different types varying from when the execution of a Web service should start to where the outcome of this execution should be delivered. Besides user preferences, this chapter argues that the computing resources on which the Web services operate have an impact on their personalization. Indeed, resources schedule the execution requests that originate from multiple Web services. To track this personalization, three types of contexts are devised, namely user context, Web service context, and resource context. A fourth type of context denoted by security enables protecting the content of each of these three contexts. The objective of the security context is to report on the strategies, which permit protecting, overseeing, and assessing the content of the contexts subject to management operations.