X-ray contrast media

An iodobenzene derivative selected from the group consisting of a compound of formula ##STR96## in which:

• R.sub.1 is selected from the group consisting of a radical having the formula ##STR97## R.sub.5 and R.sub.6 being each selected from the group consisting of hydrogen, lower alkyl, lower hydroxyalkyl and lower alkanoyloxyalkyl and a radical of the formula ##STR98## R.sub.7 being lower alkanoyl and R.sub.8 being selected from the group consisting of hydrogen, lower alkyl and lower hydroxyalkyl,
• R.sub.2 is selected from the group consisting of a radical having the formula ##STR99## in which R.sub.9 and R.sub.10 have the meanings given for R.sub.5 and R.sub.6, and a radical of the formula ##STR100## in which R.sub.11 has the meaning given for R.sub.7 or represents hydrogen and R.sub.12 has the meaning given for R.sub.8,
• at least one of the radicals R.sub.1 and R.sub.2 being of ##STR101## R.sub.4 is selected from the group consisting of hydrogen, lower alkyl and lower hydroxyalkyl,
• R.sub.15 is selected from the group consisting of hydrogen, lower alkanoyl and polyhydroxy lower alkanoyl,
• R.sub.16 is selected from the group consisting of hydrogen, lower alkyl, lower hydroxyalkyl and lower alkanoyl,
• a is 0 or 1
• n is an integer from 1 to 5
• b is 1 or 2
• and the different R.sub.2, R.sub.4 and n which exist when b = 2 may have the same or different meanings,
• a lower alkyl ester thereof and a salt with a pharmaceutically acceptable base.