This book is for all language teachers. It regards them all as materials developers in that teachers frequently have to make decisions about selecting and adapting materials, they make decisions everyday in their classrooms about how to use the materials and they sometimes develop materials of their own to supplement or even replace the materials in their course books. To help teachers to be effective materials developers, this book provides guidance in the evaluation, adaptation, and development of materials for the teaching of languages. It takes the position that language-learning materials should be principled in that they are based on what we know about how learners best learn languages. This book consists of the following five chapters: (1) Materials Evaluation; (2) Materials Adaptation; (3) Approaches to Materials Writing; (4) Aspects of Materials Writing; and (5) New Developments in Materials Writing.