Study objective: To determine whether therapeutic benefit is obtained by administering warmed IV fluid to hypothermic children. Design: Saline at 37 C in standard IV tubing was subjected to temperature measurements within a fluid warmer and at 5, 25, 45, 65, 85, and 105 cm distally. Flow rates varied from 20 to 1,000 mL/hr. Setting: The Children's Hospital of Alabama emergency department. Type of participants: None. Interventions: None. Measurements and main results: Temperature readings were made every minute until the volume required to flush the tubing had infused. Only at rates of 750 and 1,000 mL/hr did the fluid remain warmer than 32 C more than 25 cm from the warmer. Conclusion: At flow rates usual in pediatrics, hypothermic patients must be connected to fluid warmers by lengths of IV tubing shorter than customary or practical in the ED to benefit from this treatment modality.