BACKGROUND: Emergence agitation is a common side effect of sevoflurane anesthesia in preschool children. Low-dose ketamine is defined as a bolus dose of less than 1 mg/kg when administered via the intravenous route, and produces potent analgesia without respiratory depression or other side effects. In this study, we examined the effect of low-dose ketamine on the incidence of emergence agitation in preschool children receiving sevoflurane anesthesia and compared this with the effect of ketorolac. METHODS: Sixty eight preschool children receiving sevoflurane anesthesia were randomized to receive either ketorolac 1 mg/kg or ketamine 0.2 mg/kg intravenously before the end of surgery. Emergence agitation was assessed using a 3-point scale (1 = asleep, calm, or mildly agitated but easily consolable; 2 = moderately agitated or restless but inconsolable; and 3 = hysterical, crying inconsolably, or thrashing) during transfer and at 10 minutes after arrival at our postanesthesia care unit. RESULTS: We observed that the incidences of emergence agitation were 30.0%, 45.0% in the ketamine group, and 60.7%, 78.6% in the ketorolac group (P < 0.05) during transfer and at 10 minutes after arrival at the postanesthesia care unit, respectively. No significant difference was observed between the two groups with respect to discharge time from the postanethesia care unit. CONCLUSIONS: Emergence agitation after sevoflurane anesthesia in preschool children was significantly reduced by low-dose ketamine as compared with ketorolac without delaying recovery.