This document is a chapter in "The Principles and Practice of Educational Management," which aims to provide a systematic and analytical introduction to the study of educational management. The structure of the book reflects the main substantive areas of educational leadership and management, and most of the major themes are covered in the volume's 19 chapters, of which this is one. This chapter looks at recent developments in theory, research, policy, and practice in teachers' professional development and considers their implications for school leadership and management. It focuses on England and Wales because these areas offer good object lessons for autonomy, accountability, teaching and learning, strategy, and partnerships. It examines external changes in development, particularly the extensive national reforms introduced in many countries during the 1990s. These reforms resulted in extensive and radical changes in the roles and responsibilities of headteachers, other senior staff, and teachers in general. The subsequent model of professional development arising from these changes emphasized self-developing, reflective teachers in self-managing schools with devolved funding. However, the extent of the model being implemented was influenced by geography and the size of the professional development budget for a school. Other trends that affected professional development were national standards of professional practice for teachers, national curricula, performance management, and performance-related pay. None of these trends is unproblematic, and issues regarding evaluations of outcomes, the coordination of partnerships intended to promote professional development, and the question of what is the most appropriate institutional location for professional education all must be addressed. (Contains 65 references.) (RJM)