Each year, thousands of students graduate high school academically unprepared for college. As a result, approximately one-third of entering postsecondary students require remedial or developmental work before entering college-level courses. However, little is known about the causal impact of remediation on student outcomes. At an annual cost of over $1 billion at public colleges alone, there is a growing debate about its effectiveness. Who should be placed in remediation, and how does it affect their educational progress? This project addresses these critical questions by examining the effects of math and English remediation using a unique dataset of approximately 28,000 students. To account for selection biases, the paper uses variation in remedial placement policies across institutions and the importance of proximity in college choice. The results suggest that students in remediation are more likely to persist in college in comparison to students with similar test scores and backgrounds who were not required to take the courses. They are also more likely to transfer to a higher-level college and to complete a bachelor's degree.