A number of research studies during the past several years have compared the cardiovascular effects of nonionic and ionic contrast media. Nonionic media have been shown to cause less severe inhibitory effect on the conducting system of the heart and less propensity for ventricular arrhythmas. The nonionic media cause no depression in left ventricular contractile function under normal or ischemic conditions. On the contrary, ionic media produce myocardial depression and the duration and severity of this effect is greater in the ischemic state. Nonionic media cause substantially less deleterious effect on the cardiovascular system than the ionic media.