Ten patients undergoing peripheral arteriography with iopamidol were evaluated in a carefully controlled Phase I study using a variety of objective and subjective tests of discomfort. There was minimal objective evidence of pain, and the patients reported that they perceived minor discomfort and a warm sensation during the contrast injections. Five patients who had previously undergone arteriography using 2 mg of lidocaine per ml of methylglucamine diatrizoate noted a marked decrease in discomfort when iopamidol was used. Opacification of peripheral arteries was excellent. Multiple physical examinations, chemical tests, electrocardiograms, and intra-arterial pressure recordings showed that iopamidol is safe.