Obiectives : The purpose of this study was to examine the oral health knowledge and practice of elementary school children in the upper grades in a WHO healthy city for the development of oral health education programs gearing toward improving oral health care habits and oral health. The subjects in this study were 379 sixth-grade children in an elementary school in a WHO healthy city, Changwon. Methods : The questionnaire used in the study covered general characteristics with five items, oral health knowledge with 35 items and oral health care practices with 24 items. The oral health knowledge category consisted of general oral health knowledge with 13 items, knowledge on oral hygiene management with 11 items, knowledge on fluoride use with 8 items and healthy diet knowledge with 3 items. The oral health care practice category consisted of general oral health care practice with six items, practice on oral hygiene management with 11 items, practice related to fluoride use with four items, and healthy diet practice with 3 items. Results : The surveyed school children got a mean of 46.1 and 40.8 on oral health knowledge and oral health care practices, respectively out of 100 points. In the knowledge category, they scored the lowest on healthy diet knowledge with 12.6, and in the practice category, they scores the lowest on the practices related to fluoride use with 21.4. According to the regression analysis, gender had a significant impact on their oral health knowledge. The boys lagged behind the girls in that regard. Their oral health care practices were under the significant influence of knowledge level. Conclusions : Systematic education programs should be provided to prevent dental caries and promote oral health of school children, and the type of programs that stress actual oral health care is especially important.