Developmental education is one of the most difficult issues confronting community colleges. Community colleges are charged with teaching students college-level material, yet a majority of their students arrive with academic skills in at least one subject area that are judged to be too weak to allow them to engage successfully in college-level work. Thus, a majority of community college students arrive unprepared to engage effectively in the core function of the college. Colleges address this problem with extensive programs of developmental education, which are designed to strengthen skills so students can successfully complete college-level courses. In this chapter, the author first reviews evidence on the number of students who arrive with weak academic skills and the incidence of developmental education. Using longitudinal data sets that track students through their college experience, the author then reports on what happens to developmental students and reviews the research on the effectiveness of programs at community colleges designed to strengthen weak academic skills. The subsequent section briefly discusses the costs of these programs to students. The author concludes by arguing that, on average, developmental education as it is now practiced is not very effective in overcoming academic weaknesses, partly because the majority of students referred to developmental education do not finish the sequences to which they are referred. (Contains 1 figure.)