Аннотация:Mitochondria are present in all organs and tissues of the organism being responsible for the control of various aspects of the cellular function, providing the necessary supply of ATP, regulating Ca2+ signaling, controlling levels of reactive oxygen species (ROS) etc. Mitochondria perform specialized functions unique to certain tissues. Abnormalities in mitochondria disorder the key physiological functions such as the ATP production, oxidative phosphorylation, the reactive oxygen species production, and the Ca2+ regulation. This is considered as the mitochondrial dysfunction [5]. It is known that tumor mitochondria undergo some adaptive changes to further accelerate the rapid reproduction of tumor cells in an acidic and hypoxic microenvironment [2].Aims. The aims in our study were to investigate dysfunctional signs of mitochondria in tumor cells and the internal organs in mice under the growth of B16/F10 melanoma.