Professional development is supposed to increase instructional capacity in teachers. It is well funded by the Elementary and Secondary Education Act, which also provides clear expectations for activities and programs that research suggests make it effective in improving student learning (Ball & Cohen, 1999; Banilower et al., 2006; Gersten et al., 2014; Guskey, 2000; Loveless, 2014; Yoon et al., 2007). These guidelines are not commonly in practice (National Center for Education Statistics, 2012; Wei et al., 2009). Of all the actors in all the layers of the school system, principals are ideally situated to facilitate professional development that improves student learning (Hallinger & Heck, 1996; Holland, 2009; Honig & Venkateswaran, 2012; Leithwood & Louis, 2011; Sabina, 2014; Sullivan & Glanz, 2013). If principals know what research says about effective professional development for teachers, they may be better equipped to implement professional development designs that enhance student learning. This study explored the factors principals in a county in southwestern Pennsylvania take into account when choosing professional development programs for teachers. Through a survey and series of interviews, principals described their consideration of the best practices suggested by empirical research, teacher agency, adult learning theory and the limiters they face when making decisions. The study concluded that principals value engaging activities for teachers, but not the power of teacher agency in their own learning. By making decisions with teachers about the teachers' growth, principals may help balance the tension between school and district goals and the goals of their teachers as professionals. [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.]