Although volume expansion is liberally used in newborn intensive care, we know little about its effects on hemodynamics or outcomes. Given appropriately to a truly hypovolemic baby, it can be life-saving, but the clinical diagnosis of hypovolemia is probably very inaccurate. We know that volume expansion has less effect on blood pressure than dopamine, and although it seems to produce immediate increases in systemic blood flow, we do not know for how long these increases are sustained. There is evidence to show that the routine use of volume expansion in preterm babies has no effect on outcome, and there is little evidence to support its routine use during resuscitation or the treatment of metabolic acidosis. Whether crystalloids or colloids are preferable is also unclear in newborns. In situations of concern related to circulatory compromise, if possible, define the hemodynamics echocardiographically. Otherwise, if in doubt, some volume should be given, although it is probably unwise to keep expanding the volume if this is not improving physiologic (blood pressure and heart rate) or echocardiographic systemic blood flow parameters.