Studying of antiviral effect of condensed triazine derivatives--3-oxo- triazinobenzothiazine (the preparation No 1), its ribonucleoside (the preparation No 3) and ribonucleoside of its 3-thio-analogue (the preparation No 2) on reproduction of Epstein-Barr virus (EBV) in lymphoblastoid Raji cells is reported in present work. The cytotoxic action of these preparations on test cells was determined and CC50 index was 125 microg/ml for the preparation No 1, for preparation No 2 - 625 microg/ml, and for preparation No 3 - 750 microg/ml. Antiviral activity of the preparations was tested by inhibition level of accumulation of viral DNA in the cell culture, and effective concentration (EC50 index) was determined for each preparation. EC50 constituted 1 microg/ml for each triazinobenzothiazines. Selectivity index (SI) was 125 for preparation No 1, for preparation No 2 - 625, and for preparation No 3 - 750. The obtained results of studying of triazinobenzothiazines as inhibitors of EBV-infection support their high antiEBV activity and can be interesting for further investigations.