In equivalent doses for intravenous urograms conventional ionic contrast agents give iodine concentrations in the urine of approximately 30 mg iodine/ml, nonionic contrast media provide approximately 50 mg iodine/ml, and the ionic dimer Hexabrix approximately 70 mg iodine/mL. These new low osmolality, contrast media provide significantly higher urinary iodine concentrations than conventional ionic contrast media, provide better diagnostic quality excretory urograms, better patient tolerance, and fewer adverse side-effects and serious reactions. These new low osmolality, contrast media have significant advantages in intravenous urography in both safety and efficacy when compared to conventional higher osmolality contrast media.