Apoptosis is the process involved in embryonic development and homeostasis maintenance of developed organisms. Furthermore, apoptosis is the mechanism of NK and T cells (CTL) cytotoxicity. The family of bcl-2 proteins plays a crucial role in regulation of cell death and consists both of proteins with pro-apoptotic (Bax, Bad, Bid, Bik), and anti-apoptotic (Bcl-2, Bcl-xL) activity. The present work was aimed at elucidating the role of Bax and Bcl-2 expression in pathogenesis of mousepox caused by virulent Moscow strain of Ectromelia virus (ECTV-MOS) in sensitive animals - BALB/c mice (H-2ᵈ). BALB/c mice were infected via footpad with ECTV-MOS and at 5, 10 and 15 day of infection, lymph nodes, livers and spleens were isolated and subjected to further research. The tests included measurement of: apoptosis using TUNEK assay, caspase-9 activity and bcl-2 and Bax expression. The results showed: (a) influence of ECTV-MOS upon expression of Bcl-2/Bax and subsequent transduction of mitochondrial apoptotic pathway and (b) the role of Bcl-2 protein in suppression of apoptosis in Mø depending on specific immunological environment of infected organs.