Laryngoscopy and endotracheal intubation are often associated with hypertension, tachycardia and increase in catecholamines concentrations. The mechanism for these reflex cardiovas-cular changes is unknown, but may be a result of reflex sympathetic activation, involving baroreceptor system, provoked by stimulation of the epipharynx and laryngopharynx. The purpose of the present study was to determine the effect of increasing age on the changes of hemodynamic response to endotracheal intubation. We evaluated in 36 patients aged 20~79 years, ASA class I and II, given atropine sulfate 0.01 mg/kg and hydroxyzine sulfate 0.04 mg/kg I.M as premedication and thiopental sodium 5.0 mg/kg and succinylcholine chloride 1.0 mg/kg I.V. for induction of anesthesia. Patients were studied in three age group's as followings, Group I (n=12):20~39years Group II (n=12): 40~59 years Group III (n=12): 60~79 years Heart rate and blood pressure increased at endotracheal intubation in all age groups to compare with control value, there were no relationship with age in increment of blood pressure but increment of heart rate diminished with advancing age. The reason for above results is that the sensitivity to the vasoconstrictive effect of a-recep- tor stimulation is similar in all age groups, but the sensitivity to B-receptor stimulation altered cardiac chronotropic response is different with advancing age. Additionally, the diminution of sensitivity to a-receptor is not caused by decrease of density of B-receptor, but due to the impairment in the coupling of the B-receptor adenylate cyclase complex in the elderly.