The real aim of this study is to evaluate the English textbook of the third year students in Iranian high schools. What has made to carry out such a study is that so far we might not find any comprehensive and pertinent evaluation of the English textbooks instructed in Iranian high schools. Due to such paucity of English textbook evaluation, we have not yet find any prolific changes in English textbooks. The question that is going to be answered is: Does the third grade English textbook appear as a valuable textbook based on a sample of EFL students and English teachers' point of view. In order to elucidate the textbook appropriateness, this investigation is hoped to take place in different aspects such as practical considerations, layout and design, activities, skills, language type, subject and