Certain 1-(3,5-disubstituted-2,4,6-triiodophenyl)-3-(polyhydroxy-alkyl)urea compounds are useful as x-ray contrast agents. Representative of this class of compounds is the compound 3-[3-(N,N-dimethylcarbamyl)-2,4,6-triiodo-5-(N-methylcarbamyl)phenyl]-1-me thyl-1-(D-gluco-2,3,4,5,6-pentahydroxyhexyl)urea.