Homeless families, usually headed by single mothers, are the fastest growing segment of the homeless population. Although families with children make up a large percentage of those experiencing homelessness, there have been few studies on the effectiveness of services for homeless families offered by shelters transitional housing programs and other agencies. This article summarizes the research that has been conducted on families that are homeless and the limitations of this research for program evaluation. Challenges to program evaluation are identified: the lack of published studies in the area; the fact that program evaluation is rarely built into programs or funded; the methodological issues in tracking families; the difficulty in assessing the impact on families; implementation issues; the range of barriers to housing stability faced by homeless families; and changes in society at large that influence the results of evaluation. Six recommendations are made for meeting these challenges: evaluation from a coherent theory of change; setting reasonable and differential expectations for clients; strengthening linkages with other agencies that serve the same client population; increasing the emphasis on follow-up; utilizing prevention efforts to reduce the number of familites that become homeless; and working for expanded low-income housing and explanded subsidies. (abstract from the document)