In order to teach students the knowledge and skills that are required to be successful in the 21st century, teachers must change the way they have traditionally taught. A focus on problem solving, critical thinking, creative thinking, and effective communication skills is necessary for students to learn in a complex society (Darling-Hammond & Richardson, 2009). This sophisticated instruction necessitates on-going, effective professional learning for all educators. Most teachers have participated in professional development in one form or another each year; however, there is little evidence that traditional types of professional development activities increase student performance. Many conventional approaches to professional development for teachers fail to offer the ongoing support and guidance to implement new content or pedagogies and fail to provide day-to-day mentoring required of new teachers. The 21 st century has provided a whole new world of technologies that offer a wide range of professional development models for teachers (Dede, 2006). "The 'problem', simply stated, is that the future of our economy, the strength of our democracy, and perhaps even the health of the planet's ecosystems depend on educating future generations in ways very different from how many of us were schooled" (Wagner, 2008, p. xxviii). The purpose of this sequential explanatory study was to investigate teachers' perceptions of professional development and the extent to which they believe it expands their knowledge and skills and improves student learning. It also explored teachers' perceptions of alternate models of professional development. Finally, the study explored if there was a significant difference among elementary, middle, and high school teachers' perceptions of professional development. Teachers from an urban ring district in Rhode Island participated in this project. Approximately 1,000 teachers were asked to respond to an online survey questionnaire. Teachers were also invited to participate in a follow-up focus group discussion. Data from the survey questionnaires were analyzed via descriptive statistics. A thorough analysis of the content from responses to focus group questions was also completed. In general, teachers felt that effective professional development experiences had been on topics chosen by, and facilitated by, teachers. The successful experiences gave teachers the opportunity to apply what they had learned, and allowed time to meet with facilitators once again to debrief and discuss which strategies had been effective and which had not been effective. Finally, results suggested an increased awareness of how teachers perceive professional development effectiveness and whether or not teachers were aware of the availability of models different from the traditional models of professional development. This awareness may assist educators in an exploration of models that fit their learning styles thereby increasing teacher effectiveness. The results may also assist districts, policy makers, and designers of professional development in the quest for more personalized professional learning. [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.]