This resource will help school leaders and other professional development providers conduct ongoing, structured learning opportunities for mathematics teachers (K-12). The authors present models for professional development and the preparation of PD leaders designed and field-tested as part of two research projects supported by the National Science Foundation. The Problem-Solving Cycle model and the Mathematics Leadership Preparation model focus on topics of primary interest to mathematics teachers - mathematics content, classroom instruction, and student learning. They are intentionally designed so that they can be tailored to meet the needs and interests of participating teachers and schools. Through engaging vignettes, the authors describe the models, summarize key research findings, and share lessons learned. The book also includes detailed examples of workshop activities for both teachers and PD leaders.