The flow rates of the 18- to 24-gauge catheters most commonly used in pediatrics were studied to determine which catheters and infusion techniques allowed for rapid volume replacement in infants and children. As expected, short, large-diameter catheters were found to have a higher flow rate, and flows under pressure in the largest catheters tested were up to 17 times greater than in a longer, smaller diameter catheter. Catheters designed for peripheral venous insertion in children showed an 18 to 164% increase in flow rate when compared with the same gauge catheters designed for central venous use. Thus, intravenous access via a central vein does not guarantee more rapid fluid infusion unless the use of the central vein permits the insertion of a catheter larger in diameter than any that could be placed peripherally. Knowledge of the flow rates determined for the various catheters in this study will assist the physician in optimizing fluid resuscitation of the critically ill or injured child.