The potential to use mathematics so ftware to enhance student thinking and development is discussed and a taxonomy of software categories is outlined in this paper. Briefly, there are five categories of tool-based mathematics software that can be used fruitfully in a mathematics curriculum: (a) review and practice, (b) general, (c) specific, (d) environment, and (e) communication. A description of the affordances and constraints of the five types of software and how each facilitates different aspects of student learning clarifies the ways in which diverse off-the-shelf offerings can be used to address the goals of mathematics instruction, from building basic skills to exploring mathematical applications in the real world. Money spent on computers in public schools has increased at a steady rate over the last 20 years. According to the President’s Committee of Advisors on Science and Technology (1997), over $3.5 billion was spent on computers in 1997 alone (Hooper & Hokanson, 2000). Even with this increase in computers in the classroom, most instruction utilizes