The achievement of a very rapid fluid infusion rate may be critical in the resuscitation of the patient in hypovolemic shock. We studied flow rates of crystalloid and whole blood through various intravenous catheters and tubing systems. The 10-gauge Angiocath and the 8 Fr pulmonary artery introducer catheter provide flow rates equivalent to intravenous tubing (3.2 mm I.D.) inserted directly into the vein. Substantially higher flow rates can be achieved with the use of large-bore intravenous tubing (5.0 mm I.D.) connected to these catheters in place of standard intravenous tubing, allowing the infusion of 1,200-1,400 cc/minute of crystalloid and whole blood into the patient in hypovolemic shock through one intravenous catheter. Clinical trials with larger bore intravenous tubing are probably indicated.