From January 1989 to December 1989, we performed a prospective survey of adverse reactions to contrast media at three institutes of Juntendo University. We collected a total of 4365 case cards during the period. Low osmolar iodine contrast media were given in all but one case. Procedures using contrast media included computed tomography, intravenous urography, arteriography, venography and myelography. The overall incidence of adverse reactions was 6.6%, and there were no severe or fatal reactions. The incidence of adverse reactions was about the same in both sexes. However, in males, the incidence was higher in the fifth decade, and in females, it was higher in the third and seventh decades. There was no relation between the dose of contrast medium and adverse reactions. Intravenous bolus injections caused adverse reactions more often, followed by intra-arterial injections and then usual intravenous injections. The incidence of adverse reactions in patients with a history of allergy or previous reactions was higher. Pretesting was performed in 48.9% of the cases.