Abstract Background: Both hypovolemia and volume over load increase the morbidity and mortality of patients. So evaluation of intravascular volume status is the first important step in patients with signs of shock. Use of non invasive method as Inferior Vena Cava (IVC) measurements is one of methods to avoid complications of invasive procedure as central venous pressure monitoring. Aim of Study: This study aimed to provide a useful guide for noninvasive intravascular volume status (as diagnosed and manage) and to evaluating the correlation between Inferior Vena Cava-Collapsibility Index (IVC-CI) measured with ultrasonography versus central venous pressure. Patients and Methods: This study was a prospective observation study that was conducted on forty critically ill patients of both sexes, aging >!21 years old of ASA (III & IV) with signs of shock, admitted in the ICU at Al-Zahraa Uni-versity Hospitals during the last two year (October 2018 till October 2020), were enrolled in the non probability consecutive sampling after approval of the Al-Azhar University Ethical Committee and written informed consent from the patient or the 1st degree relatives in case of comatosed patient. After were screened for signs of shock, hemodynamic parameters were monitored continuously then 500ml of Nacl 0.9% was administered in 15 minutes and clinical response was observed with measures taken by using ultrasound. Then the patients were divided into responder and non responder. Results: In our study there was 24 patients of 40 patients (60%) responded to volume resuscitation. While 16 patients of 40 patients (40%) did not respond to volume resuscitation regimen and then blood pressure improved only after intro-duction of vasopressor as regarding to demographic data, there was no significant difference between two groups, as regarding to heart rate, MAP, and central venous pressure was no significant difference between two groups. In responder group there was strongly correlated that was highly significant of CVP and IVC-CI, in non responder group, there was no correlation between CVP and IVP-CI throughout the study. Conclusion: Inferior vena cava collapsibility index as-sessment is relatively safe option and sensitive at least when compared to measuring CVP.