The purpose of this study was to examine novice secondary science teachers' enactment of their teaching philosophies in their lesson planning and teaching. The framework was based on three theories: approximations of practice, teachers' knowledge of content and students (KCS), and experiential learning. The design for this research used a qualitative case study design. The participants were three novice science teachers in a large school district in the Southwestern United States. Data sources included teaching philosophies, three semi-structured interviews, lesson plans, and observations. Three research questions were: what are novice science teachers' major philosophies at the entry level of teaching; what factors influence novice science teachers' enactment of their philosophies about teaching secondary science; and how do novice science teachers implement lesson planning into their own teaching practices in a secondary science classroom? The findings suggest that novice science teachers were able to enact their teaching philosophies in their lesson plans and instructional practices, but were not able to negotiate the challenge of resistant students. The findings help to address changes that may need to be considered in the design of the teacher education program and the science methods course. Thus, this study contributes to the research on science teacher. [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.]