This protocol guided the review of research that informed the recommendations contained in the What Works Clearinghouse (WWC) practice guide "Improving Mathematical Problem Solving in Grades 4 through 8," published in May 2012. The research review involved the following steps: (1) The research staff searched the professional literature to identify relevant studies. Additional studies were identified by the expert panel; (2) Studies were screened to determine whether they were within the scope of the practice guide; and (3) Eligible studies were assessed against WWC evidence standards. This document contains information about: (1) the purpose statement that guided the work of the panel and the research team; (2) procedures for conducting the literature search; (3) eligibility criteria for reviewing relevant studies; and (4) technical issues including attrition and group equivalence.