Teachers of English find a considerable amount of literature about teaching, which would make their job easier. Part of this literature focuses on the received knowledge which is sometimes characterized by teaching theories and methods found in many books on teaching methodology. What teachers actually need more is the experiential knowledge which meets their professional needs. This book is an attempt to help teachers acquire the experiential knowledge and skills related to the teaching profession based on their needs. It focuses on developing English as foreign language teachers' competencies through an in-service professional development program following the reflective model. The competencies dealt with in this book have been drawn from teachers themselves through needs assessment. Specifically, the book has two major aims. The first is to provide a theoretical background to professional development and methodology of teaching English as a foreign language, and the second is to present a practical program which transfers such knowledge into classroom practice, i.e., the experiential knowledge.