Background. The biostimulatory and therapeutic effects of laser radiation at different wavelengths, power levels, and doses are well known, but the mechanisms underlying these effects are still not completely understood. The aim of our research was to investigate the effect of laser radiation on the function and structure of the cell membranes of human erythrocytes.Material and methods. Isolated erythrocyte cell membranes were irradiated with laser light (λ = 810 nm) of varying surface density of light energy and power. The activity of Na+, K+, and Mg2+, ATPases was used as the marker characterizing structural and functional changes in the cell membrane.Results. Laser radiation of wavelength λ = 810 nm was found to change the activity of the sodium-potassium pump in the cell membrane of human erythrocytes, while the nature of the changes turned out to be dependent on the radiation energy and power dose. The results obtained also indicate that laser irradiation induces an increase of lipid bilayer fluidity. No changes were observed in such parameters as cell stability, the level of lipid peroxidation products, reduced intracellular glutathione, or reduced oxyhemoglobin level.Conclusions. Our results indicate that laser radiation of wavelength λ = 810 nm, depending on power level and energy dosage, induces structural and functional changes in the cell membranes of human erythrocytes.