This study examined the experiences of a group of American secondary humanities teachers engaged in lesson study. Lesson study (LS) is a teacher-driven, collaborative inquiry process grounded in the realities of the classroom. It is an approach to professional development (PD) that originated in Japan, and has been credited there with contributing to improvement in teaching and learning. In contrast, most American teachers are dissatisfied with the PD available to them, and waves of reform have failed to revolutionize what happens inside many American classrooms. Some American educators have begun to utilize LS to see if its success in Japan might be replicated. American LS practice is young, and research on it is limited in important ways. The purpose of this study was to further understanding of what use lesson study may be to American education. The six participants in this research completed one LS cycle between February and April of 2008. Classroom and lesson study observations, pre- and post-lesson study interviews, and document collection were utilized to gather data. Data were analyzed using analytic induction. The researcher described in detail teachers' enactment of LS. Also, five empirical assertions were developed to explain teachers' thoughts about their LS experiences, and comment upon lesson study's potential as PD in the United States. The group departed from LS norms in several ways; some departures appeared to detract from the quality of their work. Nonetheless, the participants all valued their lesson study experiences. Specifically, they appreciated how lesson study allowed them to collaborate with their peers, and to observe and receive feedback from their students. These educators each stated a preference for lesson study in comparison to the PD typically available to them, and expressed interest in participating in lesson study again. They did, however, offer criticisms of their LS work, and expressed reservations regarding lesson study's potential in other settings. The teachers were encouraged as learners by their LS experiences, and experimented with topics that they individually connected to their lesson study work. This study's findings suggest that lesson study can help make teaching a more shared, public endeavor; provides a collaborative experience that responds to adult learners with different interests and needs; and can incrementally increase teachers' attention to student learning. Consistent with the literature, the participants' experiences suggest that lesson study is a challenging process to master. Without adequate scaffolding and support, American secondary humanities teachers may struggle to take full advantage of lesson study's potential. [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.]