Ischemic renal failure was produced in rabbits by occluding the renal arteries for 90 min. Group 1 (n = 8) received radiocontrast media at the time of occlusion, group 2 (n = 8) 24 h after occlusion, and group 3 (n = 8) 3 days after occlusion. Group 4 (n = 12) was subjected to ischemic injury alone, group 5 (n =4) served as sham-operated controls and group 6 (n = 4) did not undergo surgery but received radiocontrast media. Serum creatinine concentration in group 1 increased to a greater degree (p < 0.001) than all other groups and did not return to normal during the 8-day observation period. Creatinine concentration in groups 2, 3, 4, and 6 were comparable and significantly increased compared to sham-operated group (p < 0.05). Urinary excretion of alanine aïninopeptidase and N-acetyl-β-glucosaminidase in group 1 was significantly greater than all other groups (p < 0.05). Microscopic analysis indicated tubular necrosis was more prominent in group 1. Radiocontrast media is nephrotoxic and in the setting of ischemic injury may prevent recovery of renal function. Toxicity was dependent on the time of administration since functional impairment was not increased if dye was given 1 or 3 days after ischemic injury.