Preoperative sedation of children is a difficult problem for the psychic trauma consequent to anticipation of surgery may be as a great hazard to the patient as his original disease. Until now, a number of sedatives have been used commonly for adequate sedation of pediatric patients, but no method has been uriversally accepted. Comparison of the efficacy and safety of ketamine HCI(2.5mg/kg), hydroxyzine HCI(2 mg/kg) and pentazocine(1mg/kg) for preoperative mediaction was conducted in each 25 cases below 10 year old children for minor day out surgery. The obtained results were as follows; 1) Preoperative sedation effect was more better ketamine and hydroxyzine than pentazociae. 2) No clinically significant changes were observed in vital signs in hydroxyzine group. 3) Adverse reaction during induction of anesthesia was unremarkable in all groups, but bradycardia was occurred in pentasocine group. 4) Recovery time was more longer in hydroxyzine group than in the other groups.