Purpose: Influence of benzodiazepine (midazolam)or cholinergic inhibitor (atropine or glycopyrrlate) on intra-operative body temperature remains unclear and controversial. This study compares intra-operative body temperature in 50 abdominal surgical patients under general anesthesia between the administration of midazolam and glycopyrrolate in combination, or glycopyrrolate alone. Methods: Patients who underwent abdominal surgery were recruited from September 2008 through October 2009 at Gachon University Gil hospital in Incheon. Core body temperature was measured in the right ear using a tympanic membrane thermometer at induction of general anesthesia and at 1 hr, 2 hr, and 3 hr after induction. Results: There were no differences in core body temperature at any measurement point between either patient group (F=1.08, p=.377). Core body temperature decreased throughout the 3 hr after induction in both groups (F=9.22, p<.001). Specially, core temperatures at induction of general anesthesia (p<.001), 1 hr (p<.001), 2 hr (p<.001), and 3 hr (p<.001) after induction were lower than before administration of midazolam and glycopyrrolate, or glycopyrrolate alone. Conclusion: We conclude that a cholinergic inhibitor (glycopyrrolate, 0.1 mg) therefore seems not to affect intra-operative body temperature of patients given a benzodiazepine (midazolam, 0.04 mg kg-1), and not to increase body temperature in patients not given a benzodiazepine during the 3 hr after the induction of general anesthesia. Intra-operative warming therefore is needed to prevent hypothermia in surgical patients who receive pre-operative administration of midazolam and/or glycopyrrolate.