Cytotoxicity and anti-EBV activity ofProteflasid (SPC Ekopharm, Kyiv) in two solvents: propylene glycol (PG) and syrup--in the culture of lymphoblastoid Raji cells were studied. It was determined that cytotoxic concentration (CC50) of Proteflasid in propylene glycol was 40 microg/ml, and in syrup--150 microg/ ml; effective concentration (EC50) of Proteflasid was equal for both solvents and was 0.1 microg/ml (under therapeutic action of Proteflasid) and 0.5 microg/ml (under prophylactic action of Proteflasid). Selectivity index (SI) ofProteflasid in PG was 400 and 80 (for therapeutic and prophylactic scheme, accordingly), 1500 and 300 (for therapeutic and prophylactic scheme, accordingly) in syrup.