A study was conducted to analyze how tooth extraction procedure would affect patient's physical equilibrium sensation, using the positional centric equilibrium measuring device. Forty-five health subjects, between the ages of 20 to 30, with no systemic nor equilibrium abnormalities were selected for this study. The results obtained were as follows. 1. No noticeable changes in the centric movement were observed during the postural change from a sitting to a standing position. 2. Centric movement was transiently increased immediately after the movement from a horizontal to standing position. The average arterial pressure was decreased immediately after the alteration in body posture, suggesting that changes in body posture may influence the controlling mechanism of BP. 3. Increases in the area and velocity of the centric movement were found immediately after and up to 10 minutes after, respectively, topical administration of the anesthetic. During this time span, no correlation found between centric movement changes and circulatory changes suggested that topical anesthesia might influence the recovery reflex via central nervous system. 4. The effect of the extraction procedure on the centric movement area and the anteroposterior centric movement speed lasted for 10 minutes after extraction. On the other hand, the increase in the velocity of bilateral centric movement as well as whole body centric movement was found up to a point immediately after extraction. No correlation was found between circulatory changes and centric movement changes. It therefore was assumed that the topical anesthesia affected the recovery reflex via central nervous system.