Mathematics textbooks are critical tools for student learning in American classrooms. Teachers use them daily to plan and deliver lessons, and students use them in class to explore and learn mathematics. Given textbooks' potential to support student learning, it is important to understand how they are developed. While pressure is growing on curriculum developers and publishers to gather and share evidence of the effectiveness of textbooks, several forces are working against the production of high-quality, research-based curriculum materials. These forces include a lack of consensus on what mathematics should be emphasized at particular grade levels and a highly competitive, market-driven industry that produces textbooks under very tight time lines and, in some states, under very strict guidelines. What can and should school leaders do to select good textbook materials? This article examines the current environment and offers some advice for those considering new elementary mathematics textbooks. (Contains 1 table, 1 figure and 11 endnotes.)