The United States government devotes about $40 billion each year to means-tested housing programs, plus another $6 billion or so in tax expenditures on the Low Income Housing Tax Credit (LIHTC). What exactly do we spend this money on, why, and what does it accomplish? We focus on these questions. We begin by reviewing the history of low-income housing programs in the U.S., and then summarize the characteristics of participants in means-tested housing programs and how programs have changed over time. We consider important conceptual issues surrounding the design of and rationale for means-tested housing programs in the U.S. and review existing empirical evidence, which is limited in important ways. Finally, we conclude with thoughts about the most pressing questions that might be addressed in future research in this area. The United States federal government devotes around $40 billion each year to means tested housing programs, plus another $6 billion or so each year in tax expenditures on the Low Income Housing Tax Credit (LIHTC). This is well over twice the level of federal spending on either cash welfare or the Title I compensatory program in education, four times what is spent on the children’s health insurance fund (Falk 2012), and five times what is spent on Head Start. What exactly do we spend this money on, why, and what does it accomplish? Those are the over-arching questions at the heart of our chapter. Public concern about housing conditions among the poor dates back at least to the “muckraking” of Jacob Riis and the publication in 1890 of his book, How the Other Half Lives, which described living conditions in the Lower East Side tenements of New York City.