The chapter starts by identifying what we currently know about the overall benefits of investing in WSS (Section 5.1.). Second, we examine how such information can be used to support policymaking for identifying priority investments in WSS so as to allocate scarce financial resources to the areas that generate most benefits (Section 5.2). Finally, the chapter explores needs for additional research, at both the local and global levels in order to gather additional evidence for sound policymaking and investment in WSS (Section 5.3.). The review found that benefits have been measured at various scales, with no attempt at evaluating overall benefits except in the case of meeting the MDGs.