Rats depleted of renin by chronic saline loading are largely protected from glycerol induced acute renal failure. For some 4 h after glycerol injection, these animals showed the same apparent renal ischemia, cessation of filtration and tubule collapse seen in rats that are not renin depleted. Despite this ischemia, renal function returned rapidly, individual nephron GFR reaching 75 % of normal within the succeeding 12 h. Significant outflow obstruction was evident transiently early in recovery, but was found not to be the prime cause of the low GFR. Recovery of glomerular filtration occurred quickly despite the presence of grossly elevated hydrostatic pressure in some nephrons. It is suggested that renin depletion produced by long term saline ingestion may prevent the protracted afferent arteriolar constriction which is chiefly responsible for the pathophysiologic events in this model of acute renal failure in the rat.