As a project work on a comparative study of junior high school English textbooks in Japan, a survey was made of answers to yes/no questions. Teachers and textbooks often demand, especially at the beginning stage of language leaming, that a yes/no question be answered with yes or no and repetition of the verb or the auxiliary verb used in the question. This type of question-and-answer practice has been approved with a justification that this is an easy and useful pattern for the leamer to acquire. Recently, however, this kind of practice has been sharply criticized by those advocating the authent icity of teaching materials. In order to see the difference in the treatment of answers to yes/no questions, first, a sample of authentic materials and junior high school English textbooks were compared. Second, a comparative study of textbooks used in Japan was made on the basis of the obtained information.