Mathematics curriculum has long been a topic of keen interest in mathematics education and remains a central issue in efforts to improve mathematics learning opportunities for students. This Yearbook continues in a long line of National Council of Teachers of Mathematics Yearbooks that have addressed various facets of the changing mathematics curriculum. Although some factors such as tradition can inhibit significant change, other factors such as policy (e.g., federal No Child Left Behind legislation), societal needs (mathematically literate graduates), and technological advances (computer software, calculators) foster and accelerate the need for change. In the past year alone, a major state-initiated process for developing "common core standards" is underway. With 48 states and several territories participating in the articulation of "college and career-ready" high school graduation expectations and common K-12 standards, 2010 promises to be a landmark year of discussion and dialogue about mathematics curriculum. This Yearbook reflects some of the many issues that the field is currently discussing so it serves as both a record of current advances and a summary of challenges regarding curriculum. We hope that it will both guide and stimulate thinking about where we have been, where we are, and where we need to go. This year book is divided into five sections: (1) Curriculum Matters: Looking Back, Looking Forward; (2) The Intended Curriculum; (3) The Written Curriculum; (4) The Implemented Curriculum; and (5) Impact of Curriculum Materials on Students' and Teachers' Learning. A preface and introduction are also included.