Compounds having the structure ##STR1## wherein (Z--COO is the residue of an iodinated aromatic acid; n is an integer from 0 to 6;R.sup.1 and R.sup.2 are independently H, alkyl, fluoroalkyl, cycloalkyl, aryl, aralkyl, alkoxy or aryloxy;R.sup.3 and R.sup.4 are independently H, alkyl, fluoroalkyl, cycloalkyl, aryl, aralkyl, alkoxy, aryloxy, halogen, hydroxy or acylamino;Q represents the atoms necessary to complete a carbocyclic or heterocyclic unsaturated mono- or bicyclic aromatic ring; andR.sup.5 is H, alkyl, cycloalkyl, aryl, aralkyl, alkoxy, aryloxy, halogen, hydroxy, amino, acylamino, alkoxyalkyl, fluoroalkyl, acetamidoalkyl, COO-alkyl, cyano, carboxamido, sulfonate, sulfonamido, ureido, or carbamyl are useful as contrast agents in x-ray imaging compositions and methods.