Abstract Name : Halimah Tusakdiah Tarigan NIM : 0606102020015 Study Program: English Language Education Title : The Effect of using Student Teams Achievement Division on the students’ Passive Voice Mastery This study is aimed to investigate the effect of using STAD on the students passive voice mastery. The population of this study was grade XII year (2010-2011) students of Vocational School number 3 Banda Aceh. The total number of the population was 124 that spread in 5 parallel classes. The sample was two classes, namely XII BS as experimental group and XII PH as control group. Each class consisted of 26 students. The data were collected from both pre-test and post-test which were provided by the writer. After collecting the data, then the writer analyzed them by using t-test to know how significant the effect of using STAD on the students’ passive voice mastery was. The findings indicated that using STAD has significant effect on the students’ passive voice mastery. It was proven by the result of the t-test, which was 7.38 on df 50 and the level of significance 0.05 for two tail test. It means that t-observed (calculated) is higher than t-table (7.38 > 2.01). Since the achievement of experimental group is higher than control group so the alternative hyphothesis is accepted.