The purpose of this study were to investigate first, the effect of the preparatory educational treatment about the dental situation on infant`s dental anxiety and disruptive behavior, and second, the difference of treatment effect among infant`s dental treatment history, age, and mother`s anxiety level. The subjects for this study were 110 infants of 3-6 ages and their mothers attending at K University Hospital in Taegu city. Each subject was assigned to one of four groups accord to the dental history and preparatory educational treatment. Two variables of infant`s age and mother`s anxiety levels were with the within group variables. And the instruments of this study for measures the dependent variables were the Dental Anxiety Scale and the Disruptive Behavior Inventory with checklist, which were revised partly by this researcher. Then the preparatory education was administrated with the video program including the dental setting and treatment situation, and verbal expository by the researcher. For data analysis, one-Way and two-Way ANOVA were used to test the significance of difference. The results of the analysis indicated the followings: 1. The group experienced the preparatory education about the dental situation show the more significant decrease of dental anxiety and disruptive behavior than the control group. Therefore, the preparatory education have significant effect on infant`s dental anxiety and disruptive behavior. 2. The higher anxiety of mother is the higher infant`s dental anxiety and the higher disruptive behavior. That in, infant`s dental anxiety and disruptive behavior are not related infant`s dental history and age, but related significantly mother`s anxiety. 3. The preparatory education and the mother`s anxiety level have significant interaction on each infant`s dental anxiety and disruptive behavior. That is the effect of preparatory education on infant`s dental anxiety and disruptive behavior is more significant to higher mother`s anxiety than lower mother`s anxiety.