When antagonism to neuromuscular block is needed, glycopyrrolate is the new anticholinergic drug emplyed to counteract the muscarinic action of neostigmine. To know the effect on heart rate after an injection of glycopyrrolate and neostigmine mixture, we observed the changes in heart rate after injection of the mixtures and changing the ratio of glycopyrrolate(0.2mg/vial) to neostigmine(0.5mg/smpul) using 2 to 1, 2 to 1.5, 1 to 1, 1.5 to 2 and 1 to 2 during halothane anesthesia. The result of this study showed that the heart rates were more stable in the group given the ratio of glycopyrrolate 1 vial(0.2mg) to neostigmine 1 ampule(0.5mg) than any other gorups.