Building on the review undertaken by Berry et al. (2003) for the National Homelessness Strategy, this working paper explores some of the strategic choices faced in the conduct and commission of costing work undertaken in relation to responses to homelessness in the USA, Canada and the UK. We consider the economic arguments and research drawn upon by governments and advocacy groups to propose or justify shifts in focus from crisis to more preventive strategies, and from temporary to more permanent 'solutions' to homelessness. The paper discusses the policy and advocacy environment in which economic arguments for reform have been shaped and indicates the social and research infrastructure drawn on by researchers in the three countries. Studies that have been prominent in recent policy debate at the national level have been singled out for more detailed discussion in the attached Appendix. Our investigation provides a basis for identifying the strategic purposes of costing work in homelessness policy debate as well as drawing attention to the infrastructure of research and advocacy required to drive it in productive directions.