Postoperative pain is a significant problem that continues to be undertreated in the pediatric population. Preemptive administration of analgesics has recently emerged as a method to enhance pain management associated with surgery. The purpose of this study was to compare postoperative pain scores, rescue analgesic use, and oral fluid intake in children who received acetaminophen preoperatively to children who received postoperative acetaminophen. The sample consisted of 28 children, 2-8 years of age, scheduled for elective tonsillectomy. Children were randomized into the control or the experimental groups. Anesthesia induction and maintenance were standardized. The experimental group received 15 mg/kg of oral acetaminophen preoperatively, and the control group received 20 mg/kg of rectal acetaminophen postoperatively. Pain was scored with the FLACC (faces, legs, activity, cry, consolability) behavioral assessment tool. Scores were significantly lower for the experimental group at 30 minutes after awakening and significantly lower for the control group at 240 minutes (P < .05). Eight patients (57%) in the control group and only 4 (28%) in the experimental group required rescue morphine postoperatively. Total postoperative morphine was not significantly different between groups. There were no differences in time to initial oral fluid intake and total oral fluid intake postoperatively. Incidence of nausea and vomiting was high in both groups (64-78%). These results provide evidence that preemptive acetaminophen may enhance analgesia in pediatric tonsillectomy patients. Preoperative acetaminophen is a safe, quick, and inexpensive intervention that can readily be incorporated into anesthesia practice.