Abstract We examined the effects of indomethacin upon anesthetized control dogs and dogs in refractory hemorrhagic shock. Systemic arterial pressure, central venous pressure, cardiac output, and blood flow to the kidney, the heart, the brain, a small intestinal segment, and a piece of skeletal muscle were measured. Systemic vascular resistance and resistances of the vascular beds of the kidney, the heart, the brain, a small intestinal segment, and a piece of skeletal muscle were calculated. Blood flow distribution within the renal cortex was also examined. Indomethacin treatment had little effect upon dogs that were not in shock. Blood flow to the skeletal muscle was decreased. There was also a redistribution of blood flow within the renal cortex with a greater proportion of renal cortical flow going to the outer cortex. However, systemic vascular resistance, cardiac output, and blood flow to the heart, kidneys, brain, and small intestine were unchanged. The refractory shock state was characterized by low systemic arterial pressure and cardiac output with vascular resistance identical to control. Blood flow to the kidney and brain appears to be decreased while coronary flow is maintained. In addition, the ratio of outer renal cortical blood flow to inner renal cortical blood flow, which in the control dog was about 1.5, decreases to 1. Indomethacin treatment largely reversed the hypotension of refractory shock. The increase in arterial pressure following indomethacin treatment is the result of an increase in systemic vascular resistance. Indomethacin treatment had no effect upon cardiac output. The vascular resistances of the kidney, heart, brain, and small intestine increased following treatment of dogs in refractory shock with indomethacin. Renal blood flow was decreased 57%. The renal cortical blood flow distribution was shifted toward the outer cortex as in the controls. Substances dependent upon prosta glandin synthetase may be involved in the hypotension that is characteristic of refractory hemorrhagic shock and may be important in maintaining blood flow to the kidneys and gut.