Wiwik Nur Arifah Pengarang Arif Widyantoro, M.Pd., B.I Dosen Pembimbing 1 Niken Kencono Ungu, M.Pd Penguji 1 Buntara Adi Purwanto, S.S., M.Pd. Ketua Penguji Arif Widyantoro, M.Pd., B.I Penguji 2

This study aims to determine the effectiveness of using discourse markers(DMs) in the teaching and learning process and English speaking ability aboutopinions and thoughts for eleventh graders at SMK Purnama Wonosobo. Thisresearch uses a pure experimental design with a population of all eleventhgraders students of SMK Purnama Wonosobo, namely XI FAR A, XI FAR B,and XI AK classes totaling 70 students. The samples of this study are class XIFAR B as the experimental class (27 students) and class XI AK as the controlclass (16 students). This research used pre-test and post-test to collect data.The results show that the use of DMs is effective in the teaching and learningprocess, especially in English speaking ability. In the experimental class, theaverage pre-test score was 41.48 and the average post-test score was 79.25, sothe treatment effect was 37.7%. While in the control class, the average pre-testscore was 34.37 and the average post-test score was 41.25%, so the treatmenteffect was 6.8%. Based on the results of the analysis, it can be concluded thatthe use of DMs is effective in the teaching and learning process, especially inEnglish speaking skills. This research shows that the use of DMs can improvestudents' ability in speaking about opinions and thoughts. Therefore, the use ofDMs can be used as an effective medium in improving students' ability inspeaking English. Keywords: Discourse Markers, Teaching and Learning Process, SpeakingEnglish.