Symbiotic microbiota system functions in homeostasis maintenance of organism are performed through production of multiple microbial low-molecular-weight compounds. Short-chain fatty acids (SCFAs) have a special and multifunctional role among similar compounds. The most important SCFA is a butyric acid which provides barrier and metabolic functions mainly in large intestine. Hyperacetylasion of histones due to histone deacetylase (HDAC) inhibition is one of the key mechanisms, by dint of which the butyric acid influences biologically the large intestine atypical cells. Butyric acid influence at the molecular level is studied insufficiently, in particular, even taking into account all positive effects, there is a danger of reactivation of latent infections which are in cells in their latent form and which may enter acute lytic phase when the transcriptional apparatus is activated. This article presents the study results of butyric acid mechanisms of influence on replication process of Epstein-Barr virus in cancer cells of different origin. It is demonstrated that under the butyric acid influence in epithelial and lymphoid cells transition from latent virus phase to lytic one takes place by means of BZLF-1 and BRLF-1 genes activation. Besides, the butyric acid inhibiting effect on epithelial nasopharynx cancer cells migration in vitro is demonstrated. Based on the obtained data, conclusions were made concerning practicability of butyric acid studying for further use as a functional product in the fight against cancer.Please cite this article in press as: Astakhova L.A., Matskova L.V., Ernberg I. The studying of butyric acid influenceon Epstein-Barr virus activation in lymphoid and epithelial cancer cells.