Electron microscopic examinations of chick fibroblast cells 24 hours after inoculation with LEIV-108A and LEIV-3306 Uz strains of Baku virus revealed the following: in the nuclei of the cells infected with the LEIV-108A strain fine granular matrices were found and virus particles were forming at the periphery of the nucleus; in the LEIV-3306Uz-infected cells virus particles were found budding from the plasma membrane of the cell.