The purpose of the present study was to investigate the psychological and functional problems of malocclusion and orthodontic treatment. A total of 719 orthodontic patients (233 males and 486 females) and 555 of their parents (199 male patients, 356 female patients) without cleft lip and/or palate, orthodontic surgery or special disease were surveyed in the Department of Orthodontics at Okayama University Dental Hospital during the 15 years from 1982 to 1997. Patients and parents answered a questionnaire about psychological and functional problems of malocclusion and orthodontic treatment. The results were as follows : 1. Of the orthodontic patients, 9.4% of the males and 12.1% of the females answered that they were teased about their malocclusion, and 1.7% of the male patients and 6.8% of the female ones answered that they had negative feelings about their malocclusion. Of these patients, 58.8% became positive after orthodontic treatment. 2. Twenty-seven and nine-tenths percent of male patients and 38.7% of female patients answered that they would be at a disadvantage because of their malocclusion. Sixteen and seven-tenths percent of male patients and 32.7% of female patients were afraid that their children would have similar malocclusion. 3. Forty percent of male patients and 56.9% of female patients were ashamed of wearing metal braces, and 26.8% of male patients and 42.8% of female patients were ashamed of wearing white-colored braces. 4. Eighty-nine percent of male patients, 88.6% of female patients, 96.2% of the parents of male patients, and 94.2% of those of female patients were satisfied with the orthodontic treatment received. 5. Of the patients, 16.1% answered that they were not able to bite well before orthodontic treatment. Of these, 70.3% hoped to be able to bite better, and 79.6% of them answered that they were able to bite better, after orthodontic treatment.