The correlation between the behavioral and emotional reactions before dental treatment and the adaptability to dental treatment was evaluated in 84 three-to-six-year old children. Also the physical behavior of the children, the verbal reaction of the children and the speaking of dentists to the children during treatment were investigated among 13 cooperative and 13 uncooperative three-to-six-year old children. Dental treatment was conducted with tooth brushing, surface anesthesia, infiltration anesthesia, rubber dam application, cavity preparation with air turbine, cavity preparation with electric motor and composite resin filling. The results are summarized as follows: 1. There was a significant correlation between twelve of the twenty behavioral and emotional reactions before treatment and the adaptability to dental treatment. 2. The children who showed an uncooperative behavior to dental treatment showed a higher score of physical behavior during each treatment than the children who showed a cooperative behavior to dental treatment. 3. The score of physical behavior increased as the treatment progressed from tooth brushing to infiltration anesthesia. Among the children who showed cooperative behavior, the score showed a peak at the infiltration of anesthesia and then decreased. On the other hand, the children who showed uncooperative behavior continued showing a high score. 4. The uncooperative children showed a higher frequency of verbal reaction and crying than the cooperative children. 5. The frequency of speaking of the dentist to the uncooperative children was one and a half times as much as to the cooperative children. More than sixty percent were "instructions" and "explanations" to both of the cooperative and uncooperative children. "Praise" was used more to the cooperative children, and "count 10" and "encourage" were used more to the uncooperative children.