This study examined teachers' use of student tasks involving dynamic geometry software, in which a figure is constructed then altered while maintaining its constructed properties. Although researchers, professional organizations, and policy makers generally have been proponents of dynamic geometry for instruction, there is little research about how and why teachers implement dynamic geometry tasks for student engagement. This study sought to fill this gap. This investigation explored how and why 12 high school geometry teachers from southwestern Ohio engaged their students with dynamic geometry tasks. In addition, this study examined the teachers' enactment of such tasks in prior years and their plans for future use. Via a naturalistic inquiry design, the researcher interviewed each teacher and studied the printed dynamic geometry tasks that the teachers used with their students. The data analysis applied grounded theory methodology. The teachers had been using dynamic geometry 1-8 years, were teaching at a wide variety of schools, and were using dynamic geometry tasks in similar ways. The teachers used convergent dynamic geometry tasks (tasks for which students followed the same steps to arrive at the same results) to guide students to discover conjectures or verify theorems, to provide students with accurate dynamic visual aids, and to have a change of pace from the usual classroom routine. Many teachers experienced restricted access to computers. The teachers were proficient in what they had students do with dynamic geometry but not much beyond that, and they were interested in professional development. Teachers' present use of dynamic geometry built minimally on their past use, and it is likely that their future use will build only slightly on their present use. The researcher hypothesizes that teachers used convergent tasks due to their limited conception of high school geometry. In particular, there was a conspicuous absence of a connection to proof in the tasks. Consequently, the researcher developed a framework for dynamic geometry tasks with four phases leading to proof: construct, explore, conjecture, and prove. The researcher recommends that future investigations be conducted in conjunction with curriculum development or teacher professional development or both. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]