This chapter describes social return on investment (SROI) analysis as a method to calculate a wider concept of value of an intervention from each £1 invested, across the ‘triple bottom line’ of economic, social, and environmental value. The method is underpinned by seven principles and can be considered a practical, stakeholder adaptation of cost–benefit analysis, although there are important differences between these two methods. This chapter outlines the method, providing an illustrative case study of applying SROI analysis to housing improvements to highlight each stage of the analysis and provide a worked example of the method. The merits and limitations of this relatively new method are also discussed, including reasons for the increased use of the approach for economic evaluation of PHIs. The role of SROI in producing a pragmatic business case for prevention is also discussed.