When challenging an agreement of cession of rights (claims) one should maintain awareness of modern law enforcement practice besides good knowledge of rules, limits and restraints, provided for by law. This will allow for providing of maximum protection of interests of each of the parties, help avoiding possible mistakes, and conceive all essential terms of transactions of such kind taking into account individual peculiarities of each particular case. The article published in the magazine Corporate Lawyer No. 7 deals with some issues relevant to challenging of legal validity of agreements of cession of rights (claims), whith reference to actual court cases for illustration