Infusing fluid for performing volume expansion poses two problems. First, it inconstantly induces the increase in cardiac output that was expected from it. Second, fluid accumulation is clearly deleterious in the perioperative as in the intensive care unit settings. Thus, it is logical to perform volume expansion only after having checked that the patient is in a preload responsive state. Several tests and indices have been developed for this purpose. In this chapter, we list those that can be assessed with cardiac ultrasound. We explain their pathophysiological background, we detail the practical way they should be performed, we review their level of evidence, and we explain their respective advantages and limitations. Passive leg raising is easily performed by measuring the velocity time integral (VTI) in the left ventricular outflow tract in the semi-recumbent and in a position with the trunk horizontal and the legs elevated at 30–45°. It is well-validated but, at best, requires two operators. The respiratory occlusion tests are performed in patients under mechanical ventilation by measuring the VTI changes induced by successive 15-s end-inspiratory and end-expiratory occlusions. They require that the patient does not interrupt the respiratory occlusions. The mini-fluid challenge consists of measuring the changes in VTI induced by the infusion of 100–150 mL of fluid. The changes in VTI it induces are small and close to the minimal change that can be measured with echocardiography. The measurement must be made cautiously, and only accurate measurements should be trusted. The respiratory variation of the peak velocity in the left ventricular outflow track, which is a surrogate of pulse pressure variation, has very strict conditions of use. This is also the case for the respiratory variability of the diameter of the inferior and superior vena cava, which are the least reliable indices of preload responsiveness.