5-Amino- or 5-hydroxy-2,4,6-triiodo-1,3-benzenediacrylic and -dipropionic acids, optionally substituted by lower-alkyl or phenyl in the alpha - and alpha '-positions, are prepared by iodination of the appropriate 5-amino- or 5-hydroxy-1,3-benzenediacrylic or -dipropionic acids; and the 5-amino and 5-hydroxy groups are further substituted by acyl and alkyl groups. The iodinated compounds are useful as intravenous cholecystographic agents.