This paper discusses how researchers and others have analyzed the services histories of persons who have experienced homelessness, as well as their imputed costs. This research has been used both to make visible the ways in which the clients of mainstream social welfare systems (health, corrections, income maintenance and child welfare) become homeless and, complementarily, the impact of people who experience homelessness on the use of these service systems. Most published work in this area has been based on the integration of administrative databases to identify cases and service utilization patterns; some have used retrospective interviews. Results have been used to encourage agency administrators and policymakers to make investments in programs that reduce homelessness and/or the duration of homelessness periods. Quite recently, many local homeless services planning organizations in the US have used this approach to demonstrate the high costs of chronic homelessness and the potential cost offsets associated with the placement of people in supported housing. The opportunities and limitations associated with these various approaches, including their potential applicability to other countries and service sectors are discussed.