The invention relates to an automatic identification method for the cuff of a sphygmomanometer. A positive pressure is utilized for triggering a pulse from a valve (2) to a pressure sensing element (12) followed by measuring the width of a detected pulse. The measured pulse width is compared with a predetermined pulse width threshold value and, on the basis of this comparison, a larger and a smaller cuff are distinguished from each other, as the measured pulse width indicates the presently used cuff size.