We evaluated the pretreatment of small-dose of ketamine or normal saline in the reduction of withdrawal movements induced by rocuronium injection. One-hundred pediatric patients (aged 1–6 yr) were randomly assigned into 2 groups. A 22-gauge IV cannula was inserted into the dorsum of the hand, and ketamine 0.2 mg/kg or normal saline was given, followed by a 5 mg/kg thiopental injection 10 s later. IV rocuronium (0.8 mg/kg) was injected over 5 s. The patient’s response to rocuronium injection was graded by using a four-point scale in a double-blinded manner. We observed that the incidence of withdrawal movements was 83% in the saline group and 27% in patients pretreated with ketamine (P < 0.05). Some patients in both groups developed skin erythema at the site of injection. We conclude that pretreatment with small-dose ketamine significantly attenuates withdrawal movements associated with IV injection of rocuronium in pediatric patients anesthetized with thiopental.