Since 1979, many cases of paraganliomas in the neck have been successfully treated in Tianjin Cancer Hospital. All patients who would be subjected to this operation should undergo preoperative compressing exercises of the carotid artery to promote better circulation of collateral cerebral crossflow. Therefore, a reliable and compact instrument is necessary for the compressing exercises of the carotid artery and the long-term ambulatory monitoring of the compressing effect. This paper introduces our developed instrument, Adjustable and Digital Carotid compressor, which is based on the principle of volume-oscillometric method. During the gradual change in cuff pressure, the amplitude of consecutive arterial volume pulsation associated with pulse pressure shows change characteristically due to the nonlinearity of arterial pressure-volume (P-V) relation. Arterial pressure can be determined by detecting this change in the amplitude, while the arterial volume change can be noninvasively obtained as a function of this transmural pressure, provided that the state of blood flow are determined during this pressure measurement. Considering the simplicity and practicability of this instrument, we have designed a new portable one which consists of pulse pressure transducer, signal amplifier, peak voltage locking circuit and liquid crystal displayer. The validity and accuracy of this instrument and a few examples of its clinical application are presented.