Protein modifications in the membrane-cytoskeleton complex (MCC) of human erythrocytes, as well as changes in the intensity of reactive oxygen species (ROS) production upon cell cryopreservation with polyethylene glycol (PEG) were investigated. The protein profile of ghosts of erythrocytes frozen with PEG has common features with both the control and cells frozen without cryoprotectant. PEG makes it possible to restrict the structural rearrangements of the main MCC proteins under the effect of extreme factors and to restrain the amount of high molecular weight polypeptide complexes induced by the protein-cross-linking reagent diamide at the control level, in contrast to cells frozen without a cryoprotectant. However, changes related to the protein peroxiredoxin 2 in ghosts of erythrocytes cryopreserved with PEG are also attributed to cells frozen without a cryoprotectant that may be associated with the activation of oxidative processes. This is evidenced by a 10-fold increase in ROS formation in erythrocytes frozen under PEG protection. Thus, upon cryopreservation of erythrocytes with PEG, certain disorders in MCC proteins may be associated with increased formation of ROS, which may contribute to the disorganization of the structural components of MCC and disrupt the stability of cryopreserved cells under physiological conditions.