In 21 conscious unrestrained rabbits, arterial pressure was continuously recorded up to 11 wk by an indwelling catheter placed in the thoracic aorta. The average and standard deviation of the 24-h mean arterial pressure (MAP) were calculated and compared before and after sinoaortic denervation, sham operation, or cervical sympathectomy. At the time of sinoaortic denervation, the cervical sympathetic nerve was always disrupted bilaterally to remove possible arterial barosensory afferents contained in it. Subsequent to sinoaortic denervation performed on 12 rabbits, the average 24-h MAP was initially elevated but invariably returned to the predenervation level in 5-36 days (average 14 days). Meanwhile, the standard deviation remained elevated in all but one animal. In five sham-operated or four cervical-sympathectomized animals, neither the average 24-h MAP nor the standard deviation was significantly altered from that of controls. Our results are consistent with the view that the arterial baroreceptor reflex by itself does not play a critical role in determining the long-term level of arterial pressure.