Peer observation is an overlooked form of professional development for teachers at the secondary level. The purpose of this mixed methods study was to determine if there was a difference in attitudes between novice and veteran teachers towards the use of peer observation as a means of professional development at the secondary level. Further explored in this study were additional factors from teachers' perspectives that enhanced or hindered the use of peer observation as a form of professional development. The theoretical foundation of the study is based on adult learning theory, which states that adults need to be involved in the ongoing planning and evaluation of their learning. Quantitative data were collected using a closed-ended Likert type survey, and qualitative data were collected through face-to-face interviews. Results of "t"-test for independent samples indicated that there was no significant difference in the attitudes concerning peer observation as professional between novice and veteran teachers. Results of analysis of the qualitative data showed that teachers believed that peer observation encourages teachers to open their doors to colleagues. They believe that the impact of peer observation as a tool for change could lead to teacher collaboration, collegiality, and learning. These interactions among teachers might serve to minimize typical feelings of isolation, allow them to become more effective as they learn best practices from their colleagues, and thus might promote a more professional learning community among teachers at the school level. Creating such a professional community of effective practices would serve to positively enhance learning for students in the school. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]