Since previous studies have shown a protective effect of the administration of adenosine triphosphate-magnesium chloride (ATP-MgCl2) in shock, the present study was undertaken to determine the effect of the infusion of ATP-MgCl2 after 30 minutes of renal artery occlusion. In animals who received no infusion or only MgCl2, the combination of reduced glomerular filtration rate (GFR), marked diuresis, and reperfusion of the outer cortex suggested that these animals were in the early recovery phase of acute renal failure. In the animals who received ATP-MgCl2, there was improved GFR, no diuresis, and a normal pattern of cortical blood flow distribution. These findings would suggest that the infusion of ATP-MgCl2 appears to have either ameliorated the effect of renal ischemia, or to have accelerated the recovery process. While the precise mechanism of action of ATP-MgCl2 remains unknown, these observations may have important implications for future use in organ preservation and the management of acute renal failure. (Arch Surg 112:729-731, 1977). © 1977 American Medical Association. All rights reserved.