Application of pressure infusion bags may increase intravenous (IV) flow rates three-fold. Commercially available pressure infusers, manual squeezing of the IV fluid bag, inflating a blood pressure (BP) cuff around the bag, and kneeling on the bag have been used by prehospital personnel attempting to augment fluid infusion rates. To test the efficacy of each these methods, seven experienced paramedics were asked to employ each method in two trials using a 1-liter bag of saline through a 14-gauge, 5.7cm catheter and a standard administration set. Gravity flow from 80 cm served as the control. Pressure infusers generated flow rates of 257+/-54 ml/min and 296+/-53 ml/min when inflated to 300 mmHg and maximum pressure respectively. This rate was 2-2.5 times that of gravity flow (123+/-2 ml/min) and significantly greater than those rates obtained by any other method (p less than .0005). Manually squeezing the bag also was significantly better than was gravity flow with flow rates of 184+/-46 ml/min and 173+/-40 ml/min achieved by each of two different squeezing methods (p less than .01). Neither blood pressure (BP) cuff application and inflation (135+/-28 ml/min) nor kneeling on the bag (125+/-36 ml/min) was better than gravity alone. These results indicate that pressure infusers should be used to the exclusion of other field methods of supplying infusion pressure. If pressure infusers are not available, manually squeezing the bag is the only alternative acceptable in the field.