This Small Business Innovation Research Phase II project from Key Curriculum Press, Inc. will leverage recent understanding of Dynamic Geometry software to an emerging new category of classroom technology--handheld computers--that will greatly lower barriers to the financial, physical, and intellectual accessibility of technology across the 6-12 mathematics curriculum. The starting point for the project is The Geometer's Sketchpad (Trademark), one of the most highly regarded and commercially successful software systems presently available for math education. Reinventing Dynamic Geometry for handheld platforms will dramatically change the shape of student interactions with technology, moving these interactions away from isolated moments of technocentric computer activities conducted in a computer lab and toward a deeply-integrated learning process, wherein technology supplements and extends student learning in routine practice both inside and outside the classroom. These new contexts for technology-assisted learning in turn place new requirements upon-and create new opportunities for-educational software design. The proposed combination of an innovative hardware/software device with classroom curriculum and professional development materials to support its use will fundamentally change how teachers and students learn and do mathematics. The commercial success of The Geometer's Sketchpad development materials provide another proven avenue of commercial sustainability for the eventual products of the proposed research. demonstrates the commercial potential of Handheld Geometer's Sketchpad. The new device will have even more utility for the geometry classroom than the current incarnation of The Geometer's Sketchpad; and, if the research is successful, it will have ready application throughout the 6-12 mathematics curriculum. The enthusiastic response of teachers, students, and researchers to prototypes of software and curriculum produced during Phase I indicates that the re will be high level of teacher support. Curriculum and professional development materials provide another important avenue of commercial sustainability for the eventual products of the proposed research.