The present review is focused on the challenging problems encountered in the treatment of the inflammatory intestinal diseases, such as the loss of response to biological therapy or those associated with the transfer of the patients presenting with Crohn's disease from one medication to another. The MedLine database was employed for searching the relevant publications with special reference to the results of randomized clinical studies carried out during the past 10 years. Special attention is given to the definition of the term "escape phenomenon" and the causes behind it; methods for diagnostics of this phenomenon are discussed. Separately considered are the results of the studies on the substitution of one anti-cytokine agent failing to produce the desired effect by another (an effective one). The data obtained do not allow to directly compare the effectiveness of various anti-cytokine preparations because of different design of the studies considered. However, it can be concluded that the prescription of the second anti-cytokine medication in the absence or the loss of response to the first one constitutes an effective therapeutic modality whereas the transfer of the patients from an efficacious medicine to an alternative (less potent) agent is not recommended.