The purpose of this study is to explore the ways in which five educational leaders make use of online social network sites (SNSs) for their personal and professional learning. Specifically, I focus on how participants use social networking tools to create and maintain online learning communities, how they interact within these communities, and how they believe their use of SNSs for this purpose has benefitted their professional practice. From a post-positivist stance, the data are analyzed in light of the research on social and informal learning theory, leadership development, and the sociological paradigm of communities of practice. Using data gathered from participants' online behavior as well as through in-depth interviews, I identify common themes across participants' narratives and examine how their online behavior mirrors what the research describes as the key components of leadership development. The analysis suggests that participants interact via SNSs in ways that approximate face-to-face communities of practice. Further, the social and informal nature of participation in online communities supports learning that is relevant, timely, and contextualized--critical aspects that the research indicates are necessary for professional growth. Implications of the study findings for are explored for educational leaders and those charged with their professional development. Through this research, it is my hope that educational leaders' use of online social networks sites and their perceived benefits can be better understood. Evidence that supports that educational leaders experience real and perceived benefits as a result of participation in SNSs suggests that they may have at their disposal a tool for continuous learning and growth that is as close as their nearest computer or internet-connected device. [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.]