Abstract: objectives. This study compares the use of and cost for behavioral health ser- vices among heads of homeless and housed poor families. methods. Medicaid records for 59,135 heads of families receiving Temporary Assistance to Needy Families benefits were matched with data from Philadelphia’s municipal shelter system. Propensity score matching was used to select a matched control group to those identified as having been homeless between 1997 and 2003. Behavioral health services utilization was then assessed based on Medicaid claims records. results. Substantially higher levels of behavioral health services use and corresponding costs were found among heads of families with a history of shelter use. Conclusions. Greater use of behavioral health services by heads of homeless families may reflect greater severity of disorders or a greater likelihood to seek treatment relative to what has been suggested by previous research. Key words: Behavioral health services, homelessness, low-income families, service use, costs.