Water soluble ionic contrast media (CM) and glucose 5% were administered to Sprague-Dawley rats 36 hours after bilateral warm renal ischemia for 45 min. In all animals (n = 28) the renal ischemia caused a decrease of the absolute urinary creatinine output. Intra-arterial injection of glucose 5% or CM did not produce different patterns of absolute urinary creatinine output. The serum creatinine increased after 36 hours of reflow. When compared by means of a Mann-Whitney U-test to a normal median serum creatinine obtained in a separate group of 22 normal rats, the increase was statistically significant (p less than or equal to 0.01). The serum creatinine medians returned to a normal level after 24 hours. It seems therefore that 45 min of warm renal ischemia and 36 hours of reflow is an insufficient challenge to the rat kidney for the detection of the nephrotoxic properties of CM as opposed to when CM are injected during ischemia.