The effect of sodium metasilicate (inorganic Si) and migugen (organic Si) on the development of rice blast was studied in medium resistant and susceptible rice cultivars, Krasnodarskii 424 and Kuban 3, respectively. Rice seeds were soaked in aqueous solutions of the compounds for 1 h before sowing. The compounds were also applied to the soil before sowing and at the end of tillering. Si content in rice leaves, the intensity of the development of rice blast, and yield losses were determined as a function of the source of Si and the method of its use. The increased strength of the external membranes of epidermal cells is one of the factors of the increase in rice blast resistance in the presence of Si compounds. These cells create a mechanical barrier that prevents the penetration of the pathogen.