Urine profiles were followed for 3 or 9 days after intravenous injection of diatrizoate, iohexol or saline in 30 rats, where a tubulo-interstitial nephropathy was induced by gentamicin given over a 14-day period. Another 10 rats who had an injection of saline served as controls. Iohexol increased the excretion of lactate dehydrogenase significantly more than both saline and diatrizoate for the first 3 days, whereas diatrizoate had no effect. Both media caused significantly increased excretion of L-gamma-glutamyltransferase compared with saline, but iohexol significantly more than diatrizoate. Compared with saline S-creatinine was significantly increased following iohexol at 24 h, 3 and 9 days, and following diatrizoate only at 9 days. Among rats having gentamicin light microscopy revealed more severe changes in kidneys exposed to iohexol than to either diatrizoate or saline 3 days after their injection. Six days later no obvious differences were found between the 3 groups. In conclusion, iohexol induced more renal dysfunction than diatrizoate in this animal model of gentamicin induced nephropathy.