Iodinated contrast agents administered intravenously or intra-arterially may cause serious reactions in hypersensitive patients. Oral administration of Hypaque (diatrizoate sodium) results in minimal absorption of iodine, but the amount of iodine absorbed with Hypaque-enema studies is unreported. Hypaque-enema examinations were performed in 20 normal, nonsensitive patients and increased serum iodine levels ten to 200 times base-line values, peaking after approximately one hour in patients who had measurements obtained for four hours. Therefore, before Hypague-enema studies, patients must be carefully questioned about their tolerance of iodinated contrast agents, and preparations should be made for possible serious hypersensitivity reactions.