IntroductionIn most Iranian private language institutes, inspired by the rise of communicative language teaching, EFL teachers are widely encouraged to manage their lessons on based on a "monolingual approach" where only English is used in their classes. Some scholars have supported this approach and believe that since the process of L2 and L1 acquisition are similar, greater exposure to the L2 which results in less exposure to the L1 is essential, because the interference of L1 knowledge hinders the L2 learning process (Cook, 2001; Krashen, 1981). However, by referring to current theories on second language acquisition, it can be understood that the L1 has a necessary and facilitating role in all aspects of language teaching. Various theorists have argued against the exclusion of L1 from L2 classrooms (e.g., Nation, 2003; Larsen-Freeman, 2000) and have argued that well-considered and planned use of L1 can be positive (Cook, 2001). The use of L1 in L2 classrooms, as Mahmoudi (2011) describes it, has been a question of “to be or not to be”. He states that it is controversial because different theories of L2 acquisition offer different hypotheses about the value of L1 use in L2 classrooms. However, the role of teachers as experts in this principle must be taken into consideration. Inspired by these views, this research aims to explore Iranian EFL teachers' attitudes and perceptions towards the use of L1 in their classes at private language institutes. Problem Statement Some sympathetic EFL teachers ask whether it is acceptable or even useful to use Persian in English lessons or not. Although the literature provides us with the necessary factors to take into account when using the L1 in the classroom, it is important to consider that ...... half of the article ...... first language in the classroom. The Canadian Modern Language Review/ La Revue Canadienne des Language Vivantes, 57(3), 402-423.Kim Anh, K. H. (2010). Use of Vietnamese in English language teaching in Vietnam: Attitudes of Vietnamese university teachers. ELT Journal, 3(2).Krashen, S. (1981). Second language acquisition and second language learning. Oxford: Pergamon.Larsen-Freeman, D.(2000). Techniques and principles in language teaching. 2nd ed. Oxford: Oxford University Press.Mahmoudi, L. (2011). The use of Persian in the EFL classroom – The case of teaching and learning English at pre-university level in Iran. ELT Journal, 4(1). Nation, P. (2003). The role of the first language in foreign language learning. The Asian EFL Journal, 5(2).Nazary, M. (2008). The role of L1 in L2 acquisition: Attitudes of Iranian university students. Novitas-ROYAL, 2(2), 138-153.