This study was undertaken to determine the effects of hemorrhagic shock on cellular energy production and utilization in the lung. Energy-dependent Na+-K+ transport was measured by quantitating tissue cation changes during a cold (0.5 °C.) and a subsequent warm (37 °C.) incubation of lung slices from rats in late hemorrhagic shock and from unbled control rats. Active Na+ extrusion and K+ reaccumulation by the tissue were observed upon rewarming of lung slices from shock animals. Whereas K+ reaccumulation was not altered with shock, the rate of Na+ extrusion was approximately 40 percent higher. The measurement of the intracellular water content with cold and warm incubations showed no alterations with shock. Extracellular water increased with chilling in shock tissue but not in normal tissue. Lung tissue contents of adenosine triphosphate, adenosine disphosphate, or adenosine monophosphate were likewise unaltered. Thus cellular energy utilization or production in the lung was not damaged by hemorrhagic shock but a tendency toward increased interstitial water seemed to be present. © 1975.