The effects of sympathetic arousal level on short- and long-term habituation of the skin conductance response component of the orienting response (OR) were investigated in an experiment employing 28 subjects. Threat of shock was used to increase the arousal level of one group of subjects. These subjects were compared to a group which was not threatened by shock. Results indicated that threat of shock significantly increased tonic skin conductance level. More importantly, this increase in physiological arousal level was associated with decreased short- and long-term habituation of the OR. These results demonstrate that physiological arousal level significantly affects the habituation process.