Problem: Interdisciplinary teaming has been noted as a critical element of the middle school model associated with higher student achievement. Yet, research on middle school teams' use of common planning time suggests that the majority of meeting time is spent discussing student behavior/issues, discussing student learning problems/issues, and planning team activities with minimal time focused on matters of instructional improvement. Professional learning communities (PLCs) have been recognized in school reform literature for their potential to positively impact teaching and learning. However, limited research has specifically examined interdisciplinary middle school teams as PLCs. The purpose of this study was to explore and describe the extent to which two interdisciplinary middle school teams functioned as PLCs during the initial year of implementation and to identify factors that influenced their development. Method: A qualitative multi-case study design was employed to capture the ways in which two interdisciplinary middle school teams experienced their first year of PLC implementation. Data were collected through team meeting observations, teacher and administrator interviews, and documents. Data were organized and analyzed using Nvivo7, a qualitative research application. Further analysis was performed using case ordered matrix displays. Findings: During the first year of PLC implementation, each interdisciplinary team experimented and made meaning of the PLC process in a unique way. One team engaged in work that focused on literacy across content areas, while another team addressed more general problems of practice focused on meeting individual students' needs through student accommodations and modifications. Leadership and artifact use influenced PLC development. Administrative leaders provided direction, professional development and resources to support PLC development. Drawing upon their background expertise and PLC training, teacher leaders facilitated PLC meetings and provided guidance for their team's interdisciplinary PLC focus. Use of artifacts such as agendas and protocols helped teacher teams to maintain focus during PLC meeting times. Significance: This study has implications for how interdisciplinary middle school teams can maximize common planning times to promote instructional effectiveness and student learning across content areas. [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.]