REL Southeast developed this facilitator's guide on the topic of mathematical problem solving for use in professional learning community (PLC) settings. The facilitator's guide is a set of professional development materials designed to supplement the What Works Clearinghouse practice guide, Improving Mathematical Problem Solving in Grades 4 Through 8 (Woodward et al., 2012). The practice guide provides research-based recommendations for teachers to incorporate into their classroom practice. The facilitator's guide is designed to complement and extend the practice guide by providing teachers in a PLC setting with additional, step-by-step guidance for the best ways to implement some of these evidence-based recommendations.The facilitator's guide focuses on three of the five recommendations from the mathematics problem solving practice guide to ensure in-depth coverage of the topics and to provide ample practice opportunities and time for reflection. The three practice guide recommendations on which the facilitator's guide is based are: teach students how to use visual representations (Recommendation 3), expose students to multiple problem-solving strategies (Recommendation 4), and help students recognize and articulate mathematical concepts and notation (Recommendation 5). REL Southeast chose these three recommendations because they are interrelated and include critical content to address the two high-leverage regional needs communicated by the Improving Mathematics Instruction Research Alliance which include improving classroom discourse in mathematics and enhancing students' mathematical problem-solving skills. [This report was prepared with assistance from John Woodward. For the companion piece, "Professional Learning Community: Improving Mathematical Problem Solving for Students in Grades 4 through 8. Participant's Activities," see ED595203.]