ABSTRACTrnThis study is entitled “A STUDY ON THE ABILITY IN EXPOSITIONrnWRITING OF THE ELEVENTH GRADE STUDENTS OF SMA PGRIrnKUPANG IN THE SCHOOL YEAR 2012/2013”. It was conducted to answerrnthe following questions. 1. Are the eleventh gradestudents of SMA PGRI Kupangrnable to write exposition? 2. What is their level ability in writing Exposition? 3.rnWhat are the diffucalties encountened by the students in writing Exposition. Thernmethod used in this study was descriptive method. The subject of the study wasrnthe elevent grade students of SMA PGRI Kupang (language class). The totalrnnumber of language class was 22. The istrument used in this study was writingrnexposition test. The collected data were analyzed on five aspects of writing,rnnamelly; grammar, vocabulary, mechanics, fluency, and form. The result of thisrnstudy shows that the eleventh grade students of SMA PGRI Kupang are able tornwrite exposition writing based on the topic with the level of ability was classifiedrnas “AVERAGE” (12.86). There is no student who gets the highest score 26-30rn(excellent). There 1 student(4,54),who get score 21-25(very good),4 studentsrn(18,18) who get score 16-20(Good), 16 students(72,73) who get score 11-rn15(average), 1 (4,55)student 6-10 who get score(bad). These scores were given byrnusing analytic method offered by John Anderson. The were many errors made byrnthe students. They are grammar, followed by diction, spelling and punctuation andrnthe vocabulary. Therefore, the writer wants to give a suggestion to the Englishrnteacher of SMA PGRI Kupang, the teacher should pay more attention on thernteaching of grammar especially tenses, choice of word, punctuation, and spelling.