The purpose of this study was to investigate the impact of the mathematics anxiety treatment messages in a computer-based environment on ninth-grade students' mathematics anxiety and mathematics learning. The study also examined whether the impact of the treatment messages would be differentiated by learner's gender and by learner's prior mathematics anxiety levels (High vs. Medium vs. Low). Participants were 161 ninth-grade students, who took a required introductory algebra class in a public high school neighboring Utah State University. The learning environment was integrated with a pedagogical agent (animated human-like character) as a tutor. This study employed a pretest and posttest experimental design. Participants' mathematics anxiety was measured at the beginning and at the end of the intervention; participants' mathematics learning was measured before and after each lesson (four lessons in total). The participants were randomly assigned to work with either an agent presenting mathematics anxiety treatment messages (TR) or an agent without presenting the treatment messages (NoTR). Because of student attrition, only 128 students were included for data analysis. The results suggested that mathematics anxiety treatment messages provided by a pedagogical agent had no impact on student mathematics anxiety and mathematics learning. Second, there were no main or interaction effects of the treatment messages and learners' gender on mathematics anxiety and mathematics learning. Third, there were significant interaction effects between treatment messages and learner's prior mathematics anxiety levels only on current mathematics anxiety ( p less than 0.05 ). High-anxious students in the TR condition decreased their anxiety more than those in the NoTR condition. Medium-anxious students in the TR condition increased their anxiety whereas those in the NoTR condition decreased their anxiety. Low-anxious students in the TR condition did not change their anxiety whereas those in the NoTR condition increased their anxiety. [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.]