The assessment of the circulating blood volume is one the most important, but also the most difficult procedures when treating patients hospitalised at the intensive care unit. Since the beginning of intesive care treatement the assessment of the intravascular volume with the goal of adequate fluid management has been in the centre of modern medicine, yet only half of hemodynamically unstable patients respond to a fluid challenge. Cardiac filling pressures, such as central venous pressure and pulmonary capillary wedge pressure, have been traditionally used to assess the circulating blood volume and guide fluid management. However, studies performed during the past three decades demonstrated that cardiac filling pressures are unable to adequately assess the circulating volume and predict fluid responsiveness. Or said otherwise, static parameter central venous pressure does not provide a valid assessment of the circulating blood volume of hemodynamically unstable patients. In accordance to that, a series of minimally invasive and noninvasive monitoring technologies to assess the circulating volume using dynamic parameters has been developed. These systems measure the changes in stroke volume and pulse pressure of mehanically ventilated patients continuously using the pulse contour analysis and Doppler methods to assess the circulating volume and predict fluid responsiveness. Although the results of studies conducted so far show promissing results, further research with more patients is needed in order to adequatley evaluate the dynamic parameters in their ability to assess the circulating blood volume.