Around the time of recovery from general anesthesia we usually use atropine and neostigmine to counteract the effect of muscle relaxant that is remaining in the body. We used various kinds of combinations of atropine and neostigmine to see the effect of them on heart rate. The combinations were as follows: I) atropine 0.02mg/kg+neostigmine 0. 02mg/kg. 2) atropine 0. 2mg /kg+neostigmine 0.03mg/kg. 3) atropine 0. 02mg/kg+neostigmine 0.04mg/kg. 4) atropine 0.02mg/kg+neostigmine 0.05mg/kg. 5) atropine 0.02mg/kg+neostigmine 0.06mg/kg. 6) atropine 0.02mg/kg+neostigmine 0.07mg/kg. Ten subjects(ps.I.ASA) were taken for each combination. Thus total sample size of the six combinations were sixty, Each study has been performed in the state of ASA P.S.1, and anesthetized for b but two hours. N₂O-O₂-Halothane technique was used for anesthesia. The dosage of pancuronium was 0. 08mg/kg. The age distribution of the sample was 2 to 60, and male to female ratio was 4 to 6. We came to the following conclusions from this study. 1) Types of dosage combinations those caused little change in heart rate were; atrop!ne 0.02mg/kg+neostigmine 0.02mg/kg, and atropine 0.02mg/kg+ neostigmine 0.03mg/kg. 2) Just after the simultaneous injection of the drugs, there appeared mild tachycardia, but fifteen minutes after the administration severe bradycardia came on and, after that the heart rate returned to normal. 3) The combinations which included neostigmine, more than 0. 04mg/kg, caused severe braycardia, and the most severe bradycardia was seen with a combination of atropine 0.02mg/kg and neostigmine 0.06mg/kg.