The underlying mechanism of the low-frequency dielectric dispersion, called the alpha dispersion, of osmotically lysed erythrocytes (erythrocyte ghosts) has remained open since its finding [H. P. Schwan and E. L. Carstensen, Science 125, 985 (1957)]. The alpha dispersion is peculiar to erythrocyte ghosts and has never been observed for intact erythrocytes. Numerical calculation based on interfacial polarization revealed that the alpha dispersion is due to the presence of a hole of about 30 nm in radius in the plasma membrane.