Abstract: Compounds of the general formula: ##STR1## (where R is a group --CH(CH.sub.2 OH).sub.2 or --CH.sub.2 CH(OH)CH.sub.2 OH and A is a group --CH.sub.2 CH(OH)CH.sub.2 -- or --CH.sub.2 CH(OH)CH(OH)CH.sub.2 --) possess a package of favourable parameters which render them of particular use not only in all forms of intravascular visualisation but also in myelography.The compounds are prepared by reaction of an appropriate 5-acetylamino-N,N'-bis(hydroxypropyl)-2,4,6-triiodoisophthalamide with an agent effective to introduce the appropriate hydroxyalkylene group such as for example epichlorohydrin or 1,4-dichloro-2,3-dihydroxybutane.

Abstract: Compounds of the formula: ##STR1## wherein R represents the group --CH.sub.2 CH.sub.2 OH or --CH.sub.2 CHOHCH.sub.2 OH, particularly in racemic or optically active form, are employed as active ingredients in X-ray contrast agents for intracerebral, but particularly for vascular use. The compounds are prepared by reacting 5-(N-acetamido)-2,4,6-triiodo-N,N'-bis-(2,3-dihydroxypropyl)isophthalamide or an O-acetyl derivative thereof with an appropriate hydroxyalkylating agent and subsequently, if necessary, hydrolysing any unwanted O-acetyl groups.