One of the important functions of nervous system is to supply the information related to the injury. Therefore, for various kinds of injuries, to feel pain is thought to be the part of this important function. There are A-fiber (Type I AMHs, Type II AMHs) & C-fiber (CMHs) which respond to the mechanical & thermal stimuli as the nerve fibers of peripheral unit performing this function. The phenomena expressed to us by these stimuli are those reaction like the in- crease of heart rate and the elevation of blood pvessure by stimulation of the autonomic nervous system as well as pain. As it is, using these reactions which are the most popular parameter of pain expression during anesthesia, we make the depth of anesthesia deeper or use analgesics as adjuvants. In general, there are many kinds of analgesics for adjuvants of anesthesia or for elimination of postoperative pain. To compare the efficiency of those analgesics toward pain, the authors studied the inhibitory effects of analgesics on the increase of pulse rate and mean arterial pressure evoked by the thermal and mechanical stimulations in rats. We used the agents popularly used in nowadays 1) Tramadol HC1, known as a potent analgesics, 2) Nalbuphine, antagonist of opioids, 3) Meperidine and Morphine, opioids to com- pare the efficiency of hemodynamic augumentation by the thermal and mechanical stimulations with the control group. The results were as follows', 1) The inhibitory effects on the increase in pulse rate and mean arterial pressure evoked by the stimulations were in the decsing order of morphine, meperidine, nalbuphine, and tramadoL 2) The inhibitory effect of morphine on the incmnent of pulse rate and mean arterial pressme was evident. 3) Meperidine and nalbuphine, not so much potent as morphine in inhibitory also inhibit to a considerable degree. 4) In the case of tramadol, the increament of pulse rate evoked by the stimulations were inhibited to some extent, but it was proven not to inhibit the elevation of mean arterial pressure.