Public reporting burden for this collection of information is estimated to average 1 f»ur per response, including the time for reviewing instnjctions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of inforhiation. Postoperative pain leads to increased morbidity, length of stay, and health care costs. Several studies have shown that preemptively administered N-methyl-D-aspartate (NMDA) antagonists, such as ketamine, are effective in decreasmg perception of postoperative pain. To date, there have not been any human studies to investigate a gender difference m NMDA receptor antagonism. The purpose of this study was to compare the gender differences in the effects of preemptive ketamine on perceived pain in males and females undergomg selected ENT surgical procedures. This prospective, double-blinded study compared perceived pain in male and female subjects drawn from a convenience sample of patients at a major military medical center. Ihs surgeries there patients were presenting for were tonsillectomy, adenoidectomy, tonsillectomy and adenoidectomy (T&A) and uvulopalatopharyngoplasty (UPPP). 41 subjects were randomly assigned to either a treatment group receiving .Img/kg ketimme or a control group receiving a placebo of .9% saline. The study drug was administered between induction and incision. Pain perception following surgery was measured using a Numeric Rating Scale (NRS) on arrival to the post anesthesia care unit (PACU), and at four subsequent data points (1, 4, 12, 24 hours after PACU arrival time). ANOVA and Friedman tests were used to analyze die NRS scores. The ANOVA test did not show a significant difference (p = .768) in postoperative pam perception between males and females who received preemptive ketamine. The Friedman test did not show a significant difference (p = .27) in the level of postoperative pain perception within the groups over the five data collection points.