Accurate assessment of preload status is a major concern in the resuscitation of the critically injured patient. Of the three physiologic determinants of stroke volume, preload is the variable thai is most frequency influenced hy an insult or intervention or both in the trauma patient. In the critically injured patient, clinicians focus on the preload status to restore and maintain intravascular volume in attempts to optimize cardiac output and oxygen delivery. Untill recently, efforts to measure and optimize ventricular preload have focused on intracardiac filling pressures (central venous pressure and pulmonary artery occlusion pressure). The purpose of this review is to discuss the application of volumetric measurements that provide a more accurate means of determining recruitable ventricular preload in the critically injured patent