Though fluid administration is one of the most basic concepts in resuscitation, there is ongoing controversy and continuing research on the definition of the ideal fluid for resuscitation of trauma and hemorrhage and for intraoperative volume support. In general, crystalloids and colloids, as well as blood, blood substitutes and oxygen therapeutics, are available. This report briefly revisits the physiological mechanisms underlying resuscitation with crystalloids and colloids, emphasizing colloid-supplemented resuscitation with hypertonic saline. Finally, potential applications of oxygen therapeutics are briefly considered.