A significant challenge in higher education is to narrow the educational attainment gap between academically prepared and unprepared students. To this end, developmental or remedial education is intended to improve the academic skills and knowledge of students who are unprepared for undergraduate coursework, particularly in the areas of mathematics, reading, and writing. Arguably, developmental education may also serve a broader purpose, "to provide the minimum levels of reading, writing, and math skills deemed essential for functional participation in a democratic society and individual sustainability in a free economy" (Bahr, 2008, p. 211). Whether remedial education is effectively achieving these goals, however, has been a matter of considerable debate (Bailey, Jaggars, & Scott-Clayton, 2013; Goudas & Boylan, 2012). On the one hand, only 20% of community college students referred to developmental math and 37% of students referred to developmental reading complete a college-level course in the corresponding subject within three years (Bailey, Jeong, & Cho, 2010). Moreover, despite high rates of enrollment in developmental education, large gaps in achievement and degree completion persist (Ross et al., 2012). In California community colleges, 71% of college-ready students eventually complete a credential or transfer, compared to 41% of academically unprepared students (California Community Colleges, 2013). On the other hand, a simple comparison of success rates may not accurately portray the effectiveness of developmental education since "it is possible that developmental students would have even weaker outcomes if these services were not available" (Bailey, 2009, p. 15). Seemingly low rates of success among developmental students may be at least partly attributable to low levels of academic preparation and motivation (Bettinger, Boatman, & Long, 2013). This brief seeks to portray some of the difficulties that arise in conceptualizing remedial success rates and determining the effectiveness of developmental programs. First, the organization and cost of developmental education in the United States are described. Second, remedial enrollment rates are estimated by institutional type and various demographic attributes. Third, variation in success rates is demonstrated by categorizing students according to referral and enrollment status, course subject, severity of skill deficit, and academic intentions. Fourth, research on the effectiveness of the traditional approach is summarized, focusing on the effects of remedial assignment, enrollment, and completion. Finally, several policy implications are offered.