Synthesis and the content of RNA and protein in cells of the pig embryo kidneys infected with tick--borne encephalitis virus were studied by means of autoradiography and cytophotometry. Acceleration of synthesis and accumulation of RNA (in cellular structures) were estimated as over 125--200% of the initial level followed by a decrease in 12 hr when the virus release from the cells occurred. By the 2nd and 6--8th hr of infection (in the period of synthesis of early and late virus material), two peaks of protein contents over 123--131% were observed. The RNA and protein shifts are well correlated with the virus reproduction stages.