The purpose of this study was to investigate the kinds of adaptive techniques used by experienced and novice English language teachers in Gazi University Research and Implementation Centre for the Teaching of Foreign Languages (GURICTFL) and the reasons behind those adaptive decisions. It also aimed to explore whether there are differences between experienced and novice teachers in terms of the techniques and reasons for adaptations they make at GURICTFL. Although there are numerous theoretical discussions on teachers’ use of textbooks, teachers’ adaptive decisions, as well as their rationales for textbook adaptation, there is little practical evidence concerning these subjects. This study investigated the following research questions: 1- What kinds of adaptive techniques do the experienced and novice teachers in GURICTFL report they use? 2- What reasons do the experienced and novice teachers in GURICTFL suggest lead them to adapt the textbooks?3- Are there differences in the kinds and reasons of adaptive techniques between experienced and novice teachers in GURICTFL? The data were collected through interviews. The interviews were conducted with eight novice and eight experienced English language teachers in GURICTFL. The interviews were transcribed and the data were analysed under the categories derived from the literature. The results of the study revealed that the experienced and novice teachers used limited types of adaptive techniques when compared to the alternatives given in the literature. The most frequently used technique was addition. The adaptive techniques used by the teachers also tended to be taskspecific. The reasons for the adaptive techniques suggested by the teachers mainly focused on teachers’ beliefs and understandings, students’ needs and interests and the nature of the tasks. As to the differences between experienced and novice teachers in terms of adaptive techniques they used and the underlying reasons they gave, the results did not give a clear picture. In other words, the techniques and reasons given by both groups of teachers overlapped; however, there were minor, task-specific differences between experienced and novice teachers.The results imply that teachers adapted the textbook due to their beliefs and understandings to compensate what was lacking in the textbook in terms of the degree of teachers’ emphasis on some particular skills and tasks. The results also imply that a closer look should be taken in order to understand the relationship between textbook and curriculum implemented in GURICTFL.