Background:-The aim of intravenous (IV) fluid load administration is to improve the tissue perfusion through increasing stroke volume (SV) and cardiac  output (COP). Patients in whome COP increased by ≥ 15% are called fluid responders and those account only 50% of hypotensive patients. ^]1[ So it is very crucial to assess the fluid status of patients before fluid administration to distinguish between patients who may benefit and those who may not benefit or fluid administration is likely to be harmful in those patients. Objectives: to validate the diagnostic value of peak flow velocity in carotid artery by Doppler ultrasound in comparison to stroke volume variation (SVV) by velocity time integral (VTI) in assessment of fluid responsiveness in critically ill patients. Methods: This study is a prospective cohort study at the critical care department in Beni-Suef  university hospital ,we studied the effect of fluid challenge on 49 critically ill patients with hypotension (MAP<65mmHg). Carotid Doppler peak velocity (CDPV) and VTI measurements were obtained before and after fluid challenge. Fluid challenge responders were defined as patients whose SVV increased more than 10 % after fluid bolus by echocardiography . Results: ΔCDPV correlated significantly with an increase in SVV by VTI after fluid bolus. Area under the receiver-operator characteristic curve (AUC) of CDPV was 0.937 [95% confidence interval (CI) 0.858 – 1.00]. The optimal cut-off point of ΔCDPV for fluid responsiveness was 12.25% with a sensitivity and specificity of 90% and 94.7% respectively. Conclusion: Doppler assessment of carotid peak velocity seems to be a highly feasible and reliable method to predict fluid responsiveness in critically ill patients with hypotension (MAP> 65 mmHg)