In this preliminary study, water soluble contrast media (CM) were administrated to normal laboratory rats (n = 11) and renal function was monitored before and followed after this challenge. A significant decrease (p less than or equal to 0.001) of the absolute urinary creatinine output, was noted during 3 days after the injection of the CM: the median (M) control value was 0.0313 mumol/min. 100 g body weight (BW) (interquartile range (IR): 0.0014) while the M values the first, the second and the third day were 0.0209 mumol/min. 100 g BW (IR: 0.0141), 0.0198 mumol/min. 100 g BW (IR: 0.0044) and 0.0265 mumol/min. 100 g BW (IR: 0.0054) respectively. The serum creatinine 24 hours after injection was 59,8 mumol/l (IR: 7.92) which is significantly higher (p less than or equal to 0.002) compared to the M serum creatinine of 51.9 mumol/l (IR: 15.0) evaluated in a group of normal unchallenged laboratory rats. These changes are in contrast with the low frequency of renal failure episodes encountered in clinical circumstances. Further experiments with inclusion of a control group receiving a sham injection seem necessary.