At present time usage of radiopaque contrast agents (RCA) is indispensable part of diagnostic search in urological and oncourological patients. During it's evolution RCA's physicochemical features and terms of production improved. RCA for urographic and angiographic investigations must answer the requirements of optimal physicochemical features and biological characteristics: low plasma proteinbinding, high filtration rate, good tolerance. Visualization quality depends on the amount of injected RCA and the number of iodine atoms in the contrast agent molecule. Due to visualization improving radiopaque contrast agents molecule must contain highest possible quantity of iodine atoms, that provides better x-rays fixation. Triiodined RCA are most satisfying this requirements, however high content of iodine atoms in the molecule of contrast agent used can lead to different adverse reactions. Therefore, the ideal X-ray RCA are still not created. On a modern stage of development radiopaque contrast agents are divided into ionic and nonionic contrast agents. Nonionic RCA in its turn are subdivided into monomers and dimers. Also RCA subdivide according to their osmolarity into high-osmolar, low-osmolar and iso-osmolar radiopaque contrast agents. Introduction of low-osmolar nonionic radiopaque contrast agents made possible a decrease of amount and manifestation of adverse reactions, inherent to ionic RCA, into 3–5 times. Advantages of nonionic radiopaque contrast agents are well demonstrated particularly in debilitated patients, older patients and in patients with severe comorbidities – renal failure, diabetes mellitus, bronchial asthma, allergic conditions, also in a pediatric practice.