Minipigs (20 to 25 kg.) were subjected to bilateral renal artery occlusion for 60 minutes. Renal blood flow was reduced to 65 per cent and glomerular filtration rate to 40 per cent of normal in control animals. Administration of adenosine triphosphate with magnesium chloride intravenously immediately after the period of ischemia resulted in restoration of renal blood flow to normal and glomerular filtration rate to 74 per cent of normal 24 hours later. Bilateral renal artery occulsion for 90 minutes resulted in a more severe impairment of renal function, which was not improved by the administration of adenosine triphosphate with magnesium chloride. Adenosine triphosphate with magnesium chloride may exert its effect by improving renal blood flow through inhibition of post-ischemic intrarenal vasoconstriction or possible by enhancing restoration of intracellular adenine nucleotides. The exact mechanism remains unclear.