Besides perceptions, beliefs and metacognitive knowledge, teachers' attitude has been recognized as a significant factor in the learning process and ultimate success in a classroom (Breen {\&} Littlejhon, 2000). However, what teachers express as their attitude cannot guarantee whether they practice what they think or preach. The present study tries to find the discrepancies between what teachers believe about the tenets of Communicative Language Teaching (CLT) and what they think they do in the classroom regarding those principles on the one hand and what they actually do on the other. One hundred teachers in different branches of a famous language school in Tehran completed a questionnaire about their attitudes on different CLT principles and how often they thought they practiced those principles. However, observation of some of their classes did not show a rosy picture as far as practicing those principles was concerned; i. e. some discrepancies were observed. In the post -observation interview with some of teachers, they put forward their reasons for these discrepancies. {\textcopyright} 2010 Published by Elsevier Ltd.