In a course of the research there was studied the antiviral activity of the drug on the basis of phytosterols in the system in vitro models of the virus of Newcastle disease virus and infectious laryngotracheitis birds. The research was realized in the Republic of Belarus. As a result of realized research there was revealed that the drug had antiviral activity against pathogens in the developing chicken embryos at concentrations of 0.5x10-4 mol/l to 0.01x10-4mol/l, with the efficiency of 60-100% against Newcastle disease virus. The water soluble form of the drug on the basis of brassinosteroid in combination with beta-cyclodextrin has a virucidal action in vitro at a concentration of 0.5x10-4 mol / l with an efficiency of 60% against avian infectious laryngotracheitis virus.