THE PREVALENCE OF PARAFUNCTIONAL HABIT OF 9-11 YEARS OLD STUDENTS IN MUHAMMADIYAH WIROBRAJAN 3 ELEMENTARY SCHOOL, YOGYAKARTA Leona Ayu Adamy 1, Alfini Octavia 2 1Student of Faculty of Medicine and Health Science Universitas Muhammadiyah Yogyakarta, 2 Pediatric Department, School of Dentistry, Faculty of Medicine and Oral Science Universitas Muhammadiyah Yogyakarta Abstract Background. Parafunctional habit is a nonfunctional repetitive activity involving stomatognathic system, such us lips biting, lips sucking, and mouth breathing. This kind of habit has strong relation and influence to the growth and development of stomatognati system Aims. The Aim of this study is to assess the prevalence of parafunctional habit of 9-11 years old students in Muhammadiyah Wirobrajan 3 Elementary School. Methods. An analytical study with cross-sectional approached was carried out to 149 student who fulfilled inclusion criteria. The data were collected by questionnaire and photographs examinations, then processed by descriptive statistic in SPSS program. Chi-square test was used to compare the prevalence of parafunctional habit towards age and gender. Results. The results showed that lips biting was most commonly found (30.9%), followed with nail biting (27.5%), lip sucking (19.5%), and mouth breathing (10.7%). More than half of the sample (57.7%) has parafunctional habit. Gender has not influence towards parafunctional habit, but there was influence between age towards one of parafunctional habit. Conclusion. The prevalence of parafunctional habit of 9-11 years old students in Muhammadiyah Wirobrajan 3 Elementary School is high, and has related to age. Parafunctional habit should be stopped in order to prevent disturbances of stomatognatic disorder in the future.