Twenty-six patients with Kawasaki disease were observed in a prospective crossover study to compare coronary arteriography with a nonionic low-osmolar contrast medium, iopamidol 370 mgI/mL, and with an ionic low-osmolar contrast medium, ioxaglate 320 mgI/mL. A slight heart rate change and no severe arrhythmia during coronary arteriography were observed with both agents. Electrocardiographically, QTc elongation and ST-T changes were marked in ioxaglate and minimal in iopamidol. No ventricular fibrillation occurred with either agent. Both contrast media provided adequate visualization for the diagnosis of Kawasaki disease, but the contrast of the images and the visualization of details were better with iopamidol than with ioxaglate. Iopamidol seems to be superior to ioxaglate in pediatric coronary arteriography.