This qualitative, multicase study examined how principals perceived the role of instructional coaches and how they facilitated, influenced, and supported teachers' professional learning through the instructional coaching program. Including the researcher as a participant, 16 participants from three suburban school districts--including district-level administrators, principals, instructional coaches, and teachers--engaged in semistructured interviews. This study was framed by Desimone's core conceptual framework for professional development and Spillane's distributed leadership model. Data analysis revealed principals viewed instructional coaches as their partners in instructional leadership and professional learning facilitators. Principals facilitated and influenced the instructional coaching program by empowering teachers, promoting collaboration, and establishing a strong professional learning culture. Principals supported teaching engagement in coaching activities by clearly establishing the instructional coaching role, allowing for teaching-initiated professional learning, and ensuring coaches had the autonomy to work with teachers, including establishing goals. The findings identified several aspects of principal leadership that impacted the effectiveness of the instructional coaching program. These aspects included recognizing the importance of intrinsic motivation for professional learning and leveraging the partnership with the instructional coach to engage in their professional development and facilitate a culture of professional learning in their 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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]