To confirm the effects of atropine and neostigmine on heart rate in balanced anesthesia with tramadol (Tridol) two groups of patients who were included in class I by A.S.A. classification were studied. In group I, only atropine(1.0 mg) was given to 8 patients at the end of operation. Group 2, a mixture of atropine(1. 0 mg) and neostigmine (2.0 mg) was given to 16 patients under the same condition as group 1. The heart rate was checked every 15 seconds for 10 minntes in each group. The results were as followes:1) In group 1, about 16% increase in heart rate was manifested at 11/4 minutes after injection. After that the was no significant change in heart rate. 2) In group 2, about 19% increase in heart rate was observed at 1 minute after injection. After that 28% decrease in heart rate was noted 6 minutes after injection. After that there was no significant change in heart rate. 3) There was no significant difference between the two groups at 1 minute after injection. 4) When a mixture of atropine and neostigmine was given, atropine effect appeared earlier than neostigmine. Therefore if a mixture of atropine and neostigmine is used, we don't need to inject it very slowly in anticipation of bradycardia.5) Even though the IV route is uncertain, neostigmine triggered bradycardia can be controlled by using it mixed with atropine. because shortly after infection of the mixture no bradycardia occurs, the operator has sufficient time to correct it should it be set in later.