Ensuring student success requires a new kind of teaching, conducted by teachers who understand learning and pedagogy, who can respond to the needs of their students and the demands of their disciplines, and who can develop strong connections between students’ experiences and the goals of the curriculum. By examining information about the nature of professional development currently available to teachers across the United States and in a variety of contexts, education leaders and policy makers can begin both to evaluate the needs of the systems in which teachers learn and do their work and to consider how teachers’ learning can be further supported. NSDC has sponsored this initial report to synthesize what we know as a baseline to inform decisions and improvements in professional learning.