Collective studies offer experimental and clinical evidence for the advantages of the low osmolality agents in cardiac radiology. These agents cause less subjective discomfort, less hemodynamic and biochemical effects, and less blood pressure and rhythm disturbance in coronary angiography. The reduction of adverse effects with low osmolality media is of particular benefit to children, patients with cardiac failure, those at risk from systemic hypotension, and other high risk groups. Some coronary angiography patients and those undergoing angioplasty are probably at less risk if these media are used. No measurable clinical disadvantage in diagnostic or therapeutic cardiac radiology has been found with low osmolality contrast media.