Metallothioneins (MTs), as the low molecular weight proteins rich in the active thiol groups, whose synthesis and half-life are closely connected with the activity of zinc ions inside the cell, exert a significant influence on the antioxidant capacity of the environment within and outside the cell. MTs influence the trace elements homeostasis, contribute to the gene expression process and demonstrate the anti-apoptotic properties. They have the ability to bind and neutralize exogenous electrophilic compounds. The antioxidant property of these proteins deserve a special attention, because the MTs synthesis, during the oxidative stress in contrast to the activity of GSH and the basic antioxidant enzymes undergo a durable intensification. The human central nervous system (CNS) is particularly exposed to high concentrations of reactive oxygen species (ROS), since it consumes up to 20% of the pool of oxygen absorbed by the body. It was found that the dimension of the harmful effects of oxidative stress in the brain is inversely proportional to the MTs quantity. MTs in the human brain occur in three main isoforms: MT-1, MT-2 and MT-3. MT-1/-2 are synthesized abundantly in astrocytes. Isoform MT-3 which is characteristic for nerve cells, takes an important part in the zinc ions activity regulation, especially in the neocortical and rhinencephalic neurons. Zinc is necessary for development and the proper functioning of the human CNS. It is a potent stimulator of the MTs synthesis, and participates in the oxidation-reduction processes. MTs are also assignated to take a negative part in the malignancy process of tumors. It is assumed that the intense MTs synthesis in the neoplastic cells is a response to the persistent oxidative stress rolling within these cells and should be placed into the main mechanisms for neutralizing pro-apoptotic properties of ROS.