Atomic force microscopy was used for examination of the surface of human erythrocyte membrane after calibrated electroporation and application of pharmacological agents. Three-order surface inhomogeneities were revealed with various spectral windows of Fourier transform to elaborate the quantitative criteria to assess the state of membrane surface. The size of structural alterations induced in the membranes by electroporation was 100-300 nm, which is comparable to the size of membrane matrix.