The development of LOCM is one of the most important medical discoveries made at the end of this century. In developing nonionic compounds, Almén showed that it was possible to decrease the osmolality by a factor of 2 and also thereby reduce the chemotoxicity by as much as a factor of 20. Serious adverse side effects after the intravascular administration of contrast material are caused by a combination of osmotoxic and chemotoxic properties of an individual contrast media molecule as well as the ionic composition of the agent when in solution. Worldwide clinical experience with the use of LOCM, ionic and nonionic, consistently has shown the new material to be safer and more comfortable in clinical practice. Some form of limited use of LOCM is now part of virtually every radiologist's daily practice, and the focus is turning to the low-risk-no-risk group. There are gray areas between risk categories, with some evidence even suggesting that the 20- to 40-year-old age group may be at risk to the same or even a greater degree than other commonly accepted risk groups such as the elderly. The future promises even better and safer but, in all likelihood, expensive, contrast agents for intravascular use. The ultimate decision on choice of contrast or the fate of LOCM rests with public policy makers, organized medicine, and the individual physician and patient. Based on penetration of the marketplace (nearly 50%) in terms of LOCM sales in 1990, there is a growing awareness within our specialty as well as the public sector of the improvements offered by LOCM. It is unlikely that a major conversion back to the universal use of HOCM will ever occur. As long as cost remains the major focus of the debate over the choice, however, physicians need to be informed advocates, familiar with the science, yet sensitive to the economic implications of the decisions they make to best serve the interests of their patients.