In traumatically injured or medically unstable pediatric patients requiring resuscitation, gaining intravenous access often is frustrating for the physician and agonizing for the patient. Even when cardiopulmonary resuscitation is performed by trained professionals, cardiac arrests in children in the prehospital setting have a mortality of 79% to 100%. Immediate vascular access such as that obtained by intraosseous infusion improves survival. The intraosseous infusion technique uses the medullary cavity in the tibia as a "noncollapsible vein" for parenteral infusion. It is indicated in a child in shock or cardiac arrest when two attempts to access peripheral vasculature have failed or when more than 2 minutes have elapsed in the attempt to gain access. Epinephrine, bicarbonate, calcium, lidocaine, and volume expanders can be infused via the intraosseous route. Complications rarely occur. The technique described here is gaining acceptance in both prehospital and emergency department settings.