Purpose : This study was to describe health behavior, self-esteem, health knowledge, health education needs, and to assess the effects of health behavior on self-esteem, health knowledge and health education needs. Study Methods : A self-administrated questionnaire was carried out to randomly selected students in two middle schools in Seoul, Korea. The questionnaire contains items of health behavior on self-esteem, health knowledge and health education needs. Results : The mean score differences of health behavior were not meaningful. Health behavior had significantly positive correlation with self-esteem, health knowledge and health education needs. The multiple regression showed that higher self-esteem, health knowledge and health education needs was associated with higher scores of health behavior. Discussion : Health knowledge has a significant effect on health behavior Therefore, regular health education class must be based on health knowledge and health education needs.