A noninvasive method was developed for measuring the digital arterial pressure and the compliance by using a fingertip pneumoplethysmograph and a pneumatic cuff. The compliance (C) of the digital artery was obtained from the peak amplitude of the volume pulse wave (deltaVp-a) under the effect of the cuff pressure (Po-a) by the equation: C = deltavp-a/(Ps - P-o-a) during the dicrotic phase defined in this study. The normal mean value was 11.37 +/- 0.59 X 10(-5) cm3/mmHg. On lowering of the cuff pressure, the moment when the deltaVp value becomes positive is regarded as the systolic pressure (Ps). At the end of the dicrotic phase, the mean amplitude (deltaVss') of the pulse wave during one pulse cycle (SS') and the ratios (deltaVss'/deltaVsd), where deltaVsd is the mean amplitude of the wave during the systolic period (SD), of successive waves after a particular wave fail to increase at the same rate when the cuff pressure decreased below the diastolic pressure. The cuff pressure corresponding to this particular wave is regarded as the diastolic pressure (Pd). The mean value of the mean digital pressure of normotensive subjects was 80.6 +/- 1.2 mmHg.