The present invention refers to a process for the preparation of 5-amino-2,4,6-triiodo-1,3-benzenedicarboxylic acid, comprising the following steps: a) catalytic hydrogenation of 5-nitro-1,3-benzenedicarboxylic acid in neutral or basic environment, which gives an aqueous solution of 5-amino-1,3-benzenedicarboxylic acid sodium salt; b) direct iodination of the 5-amino-1,3-benzenedicarboxylic acid sodium salt solution deriving from step a), without further purification, with a solution of ICl in HCl, being the 5-amino-1,3-benzenedicarboxylic acid sodium salt solution previously added with HCl and H.sub.2 SO.sub.4.