With socioeconomic debelopment and change of esthetic recognaition, the demand for orthodontic treatment and number of orthodontic patients has been increasing so rapidly. And frequency of malocclusion was changed. SO this study was done in an attempt to provide an epidemiologic syudy so that we can accomodate their orthodontic needs adequately and to obtain the reliable quantitative information regarding the characrteristics of orthodonitx patients who bisied Department of Otrhodonitcs, Seoul National University Hospital from 1985 to 1994. Following results were obtained. 1. The total number of orthodontic patients of SNUDH during 1990-1994 increased in comparing with that of 1985-1989. And it showed that the number of annual patients was increasing trend. 2. The total number of female patients was 1.59 times as high as that of male. It showed that the annual perventage of female patients has been invreasing and that of male patients has been dereasing. So demands for orthodontic treatment of malocclusion of female patients were higher than that of male patients. 3. Each total perventage of class Ⅰ, class Ⅱ div.1 2 and class Ⅲ was 35.98%, 14.00%, 1.74% and 48.28%. The annual percentage of class Ⅰ group had been decreasing but it has increased at 1994. However that of Class Ⅲ group had been increasing until 1991 but it has been decreasing. 4. Each percentage of less than 6 year-old group, 6 to 8 year-old group, 8 to 12 year-old group, 12 to 188 year-old group and more than 18 year-old group was 2.65%, 8.63%, 32.50%, 27.74%, and 28.48. Annual percentage of 12 to 18 tear-old group (middle & high school students group) had been decreasing but it has been increasing. However 18 tear-old group had been increasing but it has been decreasing. So entrance examination ofr college and university is an important factor to distribution of age group.