The present study examined the changes in heart rate (HR), coefficient of variation of ECG R-R intervals (CVRR), plethysmogram (PTG) wave heigth (WH) and CV (CVWH), plasma catecholamine (pAd, pNorad), blood sugar (BS), immuno-reactive insulin (IRI) and lactate (LA) associated with gum chewing, and considered the function of autonomic nerves during gum chewing . Eleven healthy male volunteers (24.5±4.1yr.) chewed three kinds of gum which consisted of three different levels of hardness. During gum chewing in the supine position, HR increased 10-40 bpm, CVRR decreased from the resting value, and CVRR increased immediately after chewing stopped . WH decreased during gum chewing, and remained lower than the resting WH value after chewing stopped, CVWH increased during gum chwing. Catecholaminewas detected in higher concentrations after gum chewing than at rest. Moreover, pNorad was at a higher concentration, and the BS, IRI and LA concentrations roseabove the values at rest until 10 minute after all gum chewing ended . In addition, we observed a significant negative correlation between ΔpAd and ?ΔCVRR, ΔWH andΔCVWH in gum chewing exericse. These findings suggested that sympathetic nerve activity was enhanced during gum chewing, and that parasympathetic nerve activity was enhanced and sympathetic nerve activity remained enhancing slightly after gum chewing stopped.