This is a qualitative study of lesson study implementation and its impact on instructional practice in mathematics in a district in California. Four research questions guided this study: (1) What were the goals of the district and teachers as they relate to the implementation of lesson study in this case? (2) What were the relationships between the teachers' classroom instruction and goals articulated in literature on reform? (3) What were the relationships among the goals established by the district and teachers, and the goals identified in the literature on reform? (4) Did goals established at the onset manifest themselves in the classroom, and if so, how? Interviews with administrators and teachers, available artifacts, and a convenient sample of video from classroom instruction and teacher meetings immediately prior to, and immediately following instruction provided the data for the study. Common categories in the data were identified, grouped, and narrative descriptive summaries were constructed to address the research questions. Findings are presented as they relate to each research question. Because the funding source was a grant from Enhancing Education Through Technology (EETT), one goal was to include technology in the instructional process. Other goals included helping students to work collaboratively, improving teachers' questioning techniques, creating staff development opportunities, and improving lessons. Teachers also desired to increase the cognitive level of instruction, while administrators desired to improve student engagement and test scores. The district and teacher goals included goals identified in the literature on reform such as improving questioning techniques and increasing the level of rigor of instruction. While some goals such as using technology during instruction did materialize in the classroom, other goals such as improving questioning techniques and enhancing the cognitive level of instruction appeared to be more difficult to implement. Goals that reform-based documents consider most important to instructional improvement that were identified during the set-up phase were not implemented in actual instruction. Instruction remained traditional, focusing on classroom management, on a procedural approach to problem solving, and on coverage of material instead of the development of in-depth understanding. [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.]