The effects on urine and serum profiles of intravenous injection of diatrizoate, iohexol, or saline were studied in male rats pretreated with steroids or saline. Using urinary albumin, glucose, sodium, and the enzymes lactate dehydrogenase (LDH), gamma-glutamyltransferase (GGT), and N-acetyl-beta-D-glucosaminidase (NAG) as markers of glomerular and tubular function, it was found that diatrizoate caused temporary glomerular and tubular dysfunction; the effect was independent of the kind of pretreatment. Iohexol did not cause increased glomerular permeability in steroid- and saline-pretreated rats. When used following saline, iohexol induced increased excretion of three tubular components, whereas iohexol plus steroids caused increased excretion of all five tubular components. The dysfunctional effect of iohexol plus steroids was less than that of diatrizoate plus steroids. The serum components revealed no abnormalities induced by either contrast media or methylprednisolone. Pretreatment with steroids has no effect on the glomerular or tubular dysfunctional effect of diatrizoate, whereas it worsens the temporary tubular dysfunctional effect of iohexol in rats.