The need to adapt or modify the use of given textbooks and other language teaching materials to fit the requirements of particular learning situations, and even particular students, is widely recognized. This volume presents a systematic approach to adaptation useful for methods courses as well as for the experienced teacher or curriculum planner. As the first principle of effective adaptation, maintenance of congruence between a variety of factors is stressed; these factors include the teaching materials, the methodology and objectives of the course, student characteristics, the character of the language being taught, and the personality and style of the teacher. The discussion is divided into four main sections: (1) "Contextualization: The Textbook and the Real World"; (2)"Usage Problems"; (3) "Language Variety"; and (4) "Administrative and Pedagogical Concerns." The appendices present complementary studies on testbook analysis and evaluation for particular teaching-learning situations: (1) "Adapting Materials in Context," by A. Hilferty; (2) "Evaluation of Foreign Language Textbooks: A Simplified Procedure," by M. N. Bruder; (3) "Evaluating Beginning Textbooks," by A. Tucker; and (4) "Graph for Estimating Readability-Extended," by E. Fry. (AMH)