In the mid-1990s, the Chicago Public Schools declared an end to social promotion and instituted promotional requirements based on standardized test scores in the third, sixth, and eighth grades. This article examines the experience of third and sixth graders who were retained under Chicago's policy from 1997 to 2000. The authors examine the progress of these students for 2 years after they were retained and estimate the short-term effects of retention on reading achievement. Students who were retained under Chicago's high-stakes testing policy continued to struggle during their retained year and faced significantly increased rates of special education placement. Among third graders, there is no evidence that retention led to greater achievement growth 2 years after the promotional gate. Among sixth graders, there is evidence that retention was associated with lower achievement growth. The effects of retention were estimated by using a growth curve analysis. Comparison groups were constructed by using variation across time in the administration of the policy, and by comparing the achievement growth of a group of low-achieving students who just missed passing the promotional cutoff to a comparison group of students who narrowly met the promotional cutoff at the end of the summer. The robustness of the findings was tested using an instrumental variable approach to address selection effects in estimates. (Contains 7 tables and 30 notes.)