Objectives : This study was conducted in order to investigate the percentage of adolescents who brush their teeth after lunch and its related factors using raw data from the Fourth Korea National Health and Nutrition Examination Survey. Methods : In order to extract adolescents to be subjected to this study, 300 adolescents between the age of 12 to 18 who are currently attending junior and senior high school were chosen out of a total of 4,594 subjects. The results from the health surveys and the oral checkup results from the medical examination conducted on these adolescents were analyzed. Results : 1. The percentage of adolescents who brush their teeth after lunch was 33.9%. 2. The percentage of the adolescents who brush their teeth after lunch differed significantly according to the gender (p<0.001), age (p<0.05), the time of their recent visit to the dentist (p<0.05), and whether they had suffered from permanent tooth caries (p<0.05). 3. The factors which affect whether the adolescents brush their teeth after lunch was their gender, the total number of the times they brush their teeth per day, and their age. Conclusions : Effective oral health education methods should be reinforced in order to increase the percentage of the adolescents who brush their teeth after lunch.