Acute renal failure (ARF) was induced in two groups of unilaterally nephrectomized dogs by occluding the renal artery, vein, and ureter of the remaining kidney for 2 hours. The control group (Group I), had no therapy; in the experimental group (Group II), isovolemic hemodilution was carried out using 6% hydroxy ethyl starch (HES) as diluent. The hematocrit in the experimental animals was lowered from 41.62 ± 3.6% to 23.75 ± 5.2% after renal occlusion. The mean arterial pressure and the mean pulmonary arterial pressure were unchanged in either group. Cardiac output increased following hemodilution from 1.66 ± 0.35 to 2.70 ± 0.50 L/min while it remained unchanged in Group I. Control animals developed ARF characterized by progressive rise in serum creatinine concentration and death. Only 1/7 Group I animals was alive on day 7 compared to 7/7 of Group II (p< 0.01). ARF that developed initially in Group II began to resolve after day 4. There was a progressive and significant fall in serum creatinine concentration from 6.48 ± 0.67 mg/dl on day 4 to 4.08 ± 0.83 mg/dl on day 7 (p< 0.001). Immediate isovolemic hemodilution with HES can reverse ARF induced by ischemia.