This mixed methods study examined preservice secondary mathematics teachers' perceptions of a blogging activity used as a supportive teaching-learning tool in a college Euclidean Geometry course. The effect of a 12-week blogging activity that was a standard component of a college Euclidean Geometry course offered for preservice secondary mathematics teachers, during the fall semester of 2011 in a university in the western United States, was investigated in this study. The blog can be visited at: http://edsc353fall2011.wordpress.com/ Participants' perceptions were measured by two dependent variables: (1) participants' attitudes toward the blogging activity in the college Euclidean Geometry course--measured by calculating the median response to the 16 Likert-type scale items measured on a six-point scale; and (2) participants' perceived effectiveness of the blog for the learning of Euclidean Geometry--measured by calculating the median response of another 18 Likert-type scale items measured on a six-point scale. Participants' cumulative quiz scores attained on eight in-class quizzes was used as a dependent variable to see whether or not there were relationships between the quiz total and either of the other dependent variables. There were two independent variables: (1) participants' gender--a categorical variable with two categories: male and female; and (2) participants' self-reported total time spent on the Internet per week - these values were divided into two categories using a median split. Quantitative data was collected using an instrument developed by the researcher. Validity and reliability of the instrument were measured through appropriate procedures and were found to be authentic and consistent. Qualitative data was collected using two open-ended questions on the survey as well as from the students' postings to the online discussion board on the blog. The quantitative and qualitative data were analyzed separately using SPSS-PASW for Windows and MAXQDA, respectively. Participants' overall attitude scores toward the blogging activity showed a mean, median, and mode of 4.18, 4.0, and 4.0 respectively with a standard deviation of 0.95, suggesting that participants' typical response indicated that they had slightly more than positive agreement that they held a positive attitude toward the blogging activity in the College Euclidean Geometry course. Similarly for perceived effectiveness, the mean, median, mode of 4.13, 4.0, and 4.0, respectively indicated that the typical response of participants corresponds to slightly more than agreement that the blogging activity was an effective means of teaching and learning Euclidean Geometry. Due to the ordinal nature of the first two dependent variables that measure participants' attitudes toward and perceived effectiveness of the blogging activity, respectively, the non-parametric Wilcoxon-Mann-Whitney U test was carried out on median attitudes and median perceived effectiveness scores, separately, to determine if differences exist on these data across participants' gender and self-reported time on the Internet. The study did not indicate any significant difference in the participants' median attitude scores toward the blogging activity in a college Euclidean Geometry course based on their gender. Also, no significant difference was indicated in the participants' median perceived effectiveness scores of the blogging activity for the learning of Euclidean Geometry in terms of their gender. Similarly, the study did not indicate any significant difference in the participants' median attitude scores toward the blogging activity in a college Euclidean Geometry course with regard to their self-reported total time spent on the Internet per week. However, a significant difference was indicated in the participants' median perceived effectiveness scores of the blogging activity for the learning of Euclidean Geometry with regard to their self-reported total time spent on the Internet per week. Moreover, the study did not indicate a significant correlation between the participants cumulative quiz scores and their median attitude scores toward the blogging activity. Similarly, the study did not indicate a significant correlation between the participants cumulative quiz scores and their median perceived effectiveness scores toward the blogging activity. Furthermore, qualitative analyses of the survey data revealed that the preservice mathematics teachers reported numerous advantages of the blogging activity as a supportive tool in the college Euclidean Geometry course, despite the limitations of the free blog service being used. No mentionable disadvantage of using the blogging activity as a supportive tool in the college Euclidean Geometry course were found, although some minor problems of using the free blog were reported by participants. Additionally, this study analyzed the major trends that emerged in an unguided online discussion board on the blog. This component of the study revealed approximately twenty major themes raised by preservice secondary mathematics teachers. Although, the participants' discussion did not focus in any specific direction, interestingly, most of the topics were related to the improvement of learning styles and professional development, topics that are often not discussed in the classroom. (Abstract shortened by UMI.) [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.]