Research reports on the housing outcomes for persons who are homeless and mentally ill have focused on client characteristics, program type, and services as independent variables, with mired results. From social work practice, evaluation theory, and public policy perspectives, context is an important variable. Yet, it has received scant research attention in studies of the outcomes of persons who are mentally ill and homeless. This article summarizes research results from a demonstration project providing outreach or linkage services to this target population, illustrating the significant impact of context variables (site and recruitment source) on client characteristics, implementation qualitative and quantitative service assessments, and housing outcomes. The discussion suggests how these contextual factors may operate, and it goes on to make recommendations to improve social work research and practice concerning the important dimensions of context that should be assessed.