OBJECTIVE The oscillometric method is widely used for noninvasive blood pressure measurement and rarely for assessment of arterial elasticity (volume-to-pressure curve/elastogram) in the systolic (ps)/diastolic (pd) pressure interval. In a wide range of physiologically normal pressures, the elastogram is obtained mostly invasively. In the present study (in two papers), the potential of the oscillometric method for a noninvasive estimation of complete elastogram and blood pressure is examined. The aim of the present first paper is to study the relations between oscillometric arterial volume pulsations and elastogram. METHODS The interactions between transmural pressure, arterial volume pulsations, and elastogram are examined graphically on an idealized model of artery, thereafter proved on experimental oscillometric records (10 patients). RESULTS A precise determination of the transmural pressure pulsations at descendent external pressure (as in oscillometry) is presented. The basic relationships between these pulsations and arterial volume pulsations in three specific pressure zones are clarified, which allow a strict dependence to be obtained between the arterial volume pulsations envelope and elastogram. The specific cut-off of transmural pressure and arterial volume pulsations, coincidence of the arterial volume pulsations envelope with the elastogram in the ps/pd interval, and two discontinuities (jumps) of the arterial volume pulsations envelope, at ps and pd, were found. The same was observed by noninvasive arterial oscillometry in humans, with good correspondence to the model excluding narrow intervals around ps and pd, in which the jumps are not clearly distinguishable. CONCLUSIONS These specific features are assumed as elastogram attributes in the second paper, in which a noninvasive determination of both elastogram and blood pressure is carried out.