This Information Capsule reviews the research conducted on elementary level grade retention. Research findings on the effect of retention on elementary students' outcomes are inconsistent. One widely accepted conclusion is that when retention occurs, it should be accompanied by additional interventions designed to increase students' academic achievement and foster their social-emotional development. Other key research findings include: (1) Retained students are more likely to be from minority backgrounds and low-income households; (2) Retention has a temporary positive impact on student achievement; (3) No definitive conclusions have been reached on how retention affects students' academic achievement in the long-term. Most older studies found that retention had a negative impact on student's long-term achievement, but several recent studies that used more sophisticated methodologies concluded that retention had no effect, and may actually have had a positive effect, on students' future achievement; (4) Studies conducted on the impact of elementary school retention on students' high school dropout rates have reported mixed findings; (5) Research on the impact of retention on students' social and emotional adjustment has produced conflicting results; (6) Studies suggest that elementary students with the lowest levels of academic achievement and the poorest learning-related (self-regulatory) skills may have the most to gain by repeating a grade, both academically and socially; (7) Some researchers have concluded that retention is more effective at the earliest grade levels, but others maintain that retention is harmful at all grade levels; and (8) When retention is being considered for struggling elementary school students, researchers recommend that school staff implement several strategies, such as basing retention decisions on multiple criteria, using new instructional strategies and materials during the retention year, and providing students with supplemental academic and social-emotional interventions.