A prototype large-bore intravenous tubing was developed and tested. Mean flow rates for blood (Hct 45%) and tap water were determined for several catheters at 600 mm Hg, 300 mm Hg, and gravity flow and were statistically analyzed by calculating the 95% confidence intervals. The degree of hemolysis during high pressure and flow was determined by measuring the plasma free hemoglobin using the spectrophotometric method. To determine if cold. banked blood can be adequately warmed at high flow rates, thermocouples were used to measure the blood temperature before and after rapid infusion through a bloodwarmer. Results included maximum flow rates of 1,764 mL/min for tap water, and 1,714 mL/min for blood (Hct 45%) at 600 mm Hg through the large-bore tubing and an 8.5-F catheter. Flow rates for other pressure and catheter combinations were tabulated. The plasma-free hemoglobin increased slightly compared to controls with high pressure (<~ 600 mm Hg) and flow rates. The increase correlated with less than 1% red blood cell Iysis in all trials. When 13 C blood was infused through a warmer, blood temperature increased to 25.3 C at the maximum flow rate of 732 mL/min. Slightly higher heat gain resulted with slower infusion rates. We conclude that the prototype large-bore tubing and up to 600 mm Hg pressure provide rapid flow rates without significant hemolysis. Blood warming may be inadequate at higher flow rates.