The author reviews the clinical, ethical, medicolegal, and economic consequences of the routine versus limited use of low-osmolar contrast media for patients undergoing urographic and other radiologic studies. A comprehensive review of the literature since the introduction of low-osmolar contrast media was conducted, focussing on medical decision making and the economic impact of those decisions on radiologic studies requiring the administration of water-soluble contrast agents. Compared with high-osmolar ionic contrast media, routine use of low-osmolar agents for intravascular injection during diagnostic imaging results in fewer idiosyncratic reactions in patients and potentially less renal injury in a subgroup of critically ill patients. The high cost of low-osmolar agents relative to the overall cost of the examination has prevented the universal adoption of this class of agents in the United States. Economic pressures on private and government-based insurance plans, as well as on managed-care systems responsible for a variety of patient populations, continue to limit the availability of low-osmolar agents to the individual patient.