Millions of radiologic examinations requiring the use of iodinated contrast are performed yearly in North America. Triiodobenzoic acid, the contrast agent molecule currently in use, is a benzene ring covalently bonded to the 3 iodine atoms. Iodinated contrast media can be divided in 4 categories: ionic monomers, ionic dimers, nonionic monomer, and nonionic dimers. Currently, second- and third-generation nonionic low-osmolar and iso-osmolar contrast media are used in clinical practice. The search for a safer and more effective iodinated contrast agents remains an ongoing challenge and important research topic.