Hypotension is common during surgery in patients under anesthesia and may cause organ underperfusion and ischemia. After induction of general anesthesia, patients are at particular risk of developing hypotension because of the cardiovascular depressant and vasodilatory effects of anesthetic agents, as well as lack of surgical stimulation. Furthermore, patients may have preexisting hypovolemia resulting from dehydration and impaired compensatory responses, which increase the risk. Severe episodes of intraoperative hypotension have been proposed as an independent risk factor in the development of postoperative adverse outcomes such as myocardial infarction, stroke, heart failure, acute kidney injury, prolonged hospital stay, and even increased 1-yr mortality rates both in patients undergoing cardiac surgery and in those undergoing noncardiac surgery. Predictors of hypotension after induction of anesthesia include American Society of Anesthesiologists physical status (ASA) III and IV, baseline mean arterial pressure lower than 70 mmHg, age more than 60yr, use of high fentanyl dose. Heart rate (HR) variability can predict hypotension and bradycardia after induction of anesthesia. However, the role of preoperative volume status in the development of hypotension after induction will not been assessed fully. A surgical patient’s preoperative volume status may vary due to physical status, comorbidities, and preoperative treatments such as bowel preparation and fasting, and these contributory factors have been shown to have an influence on the patient’s susceptibility to intraoperative hypotension. Assessing intravascular volume status is a challenge for clinicians. Traditional static parameters such as central venous pressure have been criticized for invasiveness and lack of accuracy. A number of dynamic parameters that assess volume status have been recommended recently. Ultrasound measurements of inferior vena cava (IVC) diameter with respiration, which include (1) maximum diameter of the IVC (dIVCmax) at the end of expiration during spontaneous respiration and (2) collapsibility index (CI), have been recommended as rapid and noninvasive methods for estimating volume status. These parameters have been proposed as repeatable and easily obtainable parameters by operators with little experience in echocardiography. Ultrasound measurement of the IVC has been studied extensively as a predictor of fluid responsiveness in different clinical settings, and several studies have demonstrated that dIVCmax and CI are reliable indicators of intravascular volume status. Therefore, we hypothesized that preoperative dIVCmax and its respiratory variation, that is, CI, could predict the incidence of hypotension after induction of general anesthesia.