Published language materials are widely used around the world, but many Foreign Language (FL) and/or Second Language (SL) learners still fail to develop their communicative competence satisfactorily and they are still not happy with their language materials. Materials design has recently been characterized by two important developments: first, published materials are now used more widely than ever before; second, and it is this which makes the spread of published materials very significant, materials themselves have evolved into much more complex objects. Therefore, there is a need to develop a principled framework for evaluating and developing the language materials in a comprehensive approach. In this article, the author starts the discussion with the importance of English language materials and the process of materials evaluation. After that the author will elaborate on a potential design for developing a principled framework for materials evaluation. Implications of the framework and its contribution to the field of applied linguistics have been also elaborated.