The use of L1 in L2 classess has long been a controversy. Krashen (1985) proposed that to succeed in L2 learning, L2 should be exposed extensively. Furthemore, he argued that failure in exposure of L2 is caused by available access to use L1. To argue Krashen’s theory, numerous researchers point out that the use of L1 in L2 classess turns out to be beneficial. Among them are Cook (2001) and Tang (2000) who asserted that L2 learning and comprehension increase when L1 is occasionally used. This research aims to reveal the role of L1 (Indonesian language) by both teachers and learners in English classrooms at tertiary level. The data were obtained from questionnaires distributed to 158 students and 23 teachers at Muhammadiyah University of Yogyakarta. Interviews were also conducted to 5 teachers. The findings show that 93 students and 16 teachers state that L1 should be used in their class. Most students (138) state that L1 should be used when explaining difficult concepts of L2, and this is in line with 22 teachers who admitted that they use L1 when explaining difficult concepts.64 students and 14 teachers state that they are sure enough that using L1 in an English class helps learners ‘ learning process. The overall findings suggest that L1 should be used in L2 classess,since its absence may hinder learners’ learning process. Thus, Krashen’s theory on giving maximum exposure by not providing access to use L1 does not work in this particular context. Key words: L1 use, L2 classes,tertiary level