This review protocol guides the review of research that informs the What Works Clearinghouse (WWC) "Assisting Students Struggling with Mathematics: Intervention in the Elementary and Middle School Grades" practice guide. The mathematics intervention practice guide will be an update of the original practice guide, "Assisting Students Struggling with Mathematics: Response to Intervention (RtI) for Elementary and Middle Schools," published in 2009. This update is in response to the nature and quantity of research in the field and an increased interest in interventions for students struggling in mathematics. Over the last 10 years, there has been an increase in rigorous research in Grades K-8 addressing interventions that could be used in Multi-tiered Systems of Support (MTSS). The intervention research has focused on a range of mathematical topics (e.g., fractions, ratios, proportional reasoning). The updated practice guide, like the original guide, will focus on the most effective instructional practices in mathematics for the target population--students in kindergarten through Grade 8 who struggle learning mathematics (i.e., students with mathematics difficulties [MD] or students with learning disabilities in mathematics [MLD]).