A system for calibration-free cuff-less evaluation of blood pressure is proposed. The system includes an ultrasound-based arterial compliance probes and a controller unit connected to the said probe. The ultrasound transducers measure the change in arterial dimensions, pulse wave velocity, and other character traits of an arterial segment over continuous cardiac cycle, which is then used to evaluate blood pressure parameters without any calibration procedure using dedicated mathematical models. The pressure sensor/force sensor/biopotential transducers/accelerometric sensors measure a pressure acting on a skin surface at a measurement site, an internal arterial transmural pressure level, an applied pressure or a hold-down pressure on the skin surface or an arterial site, biopotential and/or plethysmograph signal, arterial vibrations acting on the measurement site as a function of the arterial pressure and the mechanical characteristics and/or a function of the applied/hold-down pressure and/or function of external factors.