This study was attempted to explore the relationship between locus of control and the discomfort of the patients at the initial stage of the orthodontic treatment. Locus of control was measured by ‘Locus of Control(LOC) scale for children’ and ‘Orthodontic Locus of Control(OLOC) scale for children’. The discomfort was measured by ‘discomfort index card’ in 52 children and adolescent patients who initiate orthodontic treatment. In addition, ‘locus of control of the patients’ mothers was measured by ‘Orthodontic Locus of Control(OLOC) scale for parents’. The results were as follows : 1. The test-retest reliability of ‘Locus of Control(LOC) scale for children’ and ‘Orthodontic Locus of Control(OLOC) scale’ was in the moderate to high range. 2. Out of 52 patients, 47 showed moderate to severe discomfort following placement of an initial archwire. The patients showed the most severe discomfort on the first day, and most of the discomfort was manifested within the first 3 days, then decreased until the 7th day. There was no significant difference in the discomfort according to sex and age. 3. The discomfort of the patients was the highest in the morning session when a day was divided into 4 sessions, i.e., morning, afternoon, evening, and night. 4. In the score of ‘Locus of Control(LOC) scale for children’ and ‘Orthodontic Locus of Control(OLOC) scale for children’, the group of internal locus of control expressed more discomfort than the group of external locus of control. And there was no significant correlation between locus of control of the patients and that of their mothers. 5. There was no significant difference in the score of locus of control according to sex and age. However, the score of boys tended to be lower than that of girls and the score of primary school students higher than that of middle and high school students.