To date, there has been very little research-based mathematics curriculum for talented elementary students. Yet the gifted education and mathematics literature suggest support for curriculum that is both enriched and accelerated with a focus on developing conceptual understanding and mathematical thinking. Project M[superscript 3]: Mentoring Mathematical Minds is a 5-year Javits research grant project designed to create curriculum units with these essential elements for talented elementary students. These units combine exemplary teaching practices of gifted education with the content and process standards promoted by the National Council of Teachers of Mathematics. The content at each level is at least one to two grade levels above the regular curriculum and includes number and operations, algebra, geometry and measurement, and data analysis and probability. The focus of the pedagogy encourages students to act as practicing professionals by emphasizing verbal and written communication. Research was conducted on the implementation of 12 units in 11 different schools, 9 in Connecticut and 2 in Kentucky. The sample consisted of approximately 200 mathematically talented students entering third grade, most of whom remained in the project through fifth grade. Students in this study demonstrated a significant increase in understanding across all mathematical concepts in each unit from pre- to posttesting. Thus, Project M[superscript 3] materials may help fill a curriculum void by providing appropriate accelerated and enriched units to meet the needs of mathematically talented elementary students. (Contains 3 tables and 1 footnote.)