Results of experimental and theoretical studies of unmagnetized stochastic motion of the plasma sheet electrons and the mixing of plasma in the plasma sheet are presented. Analysis of the electron temperature distributions within the plasma sheet is undertaken using the data from Intercosmos-Bulgaria-1300 polar orbiting satellite. The electron temperature is obtained with consideration of acceleration of precipitating electrons by the field-aligned potential drop; this temperature is nearly constant in the meridional direction and has no longitudinal dependence during quiet geomagnetic conditions. Analysis of spacial fluctuations of precipitating electron fluxes for a fixed electron energy shows that fluctuation spectra of primary electrons have a power dependence and resemble the spectra of electric field fluctuations observed within the plasma sheet. The satellite observations are interpreted in terms of stochastic motion of the plasma sheet electrons and intensive mixing of plasma in the sheet. It is suggested that the electron motion in the electric field with a characteristic scale comparable with the electron Larmor radius is a source of stochastization; chaotization of the particle trajectories could be a part of stochastization process. The particle motion in a homogeneous magnetic field and in a regular inhomogeneous electric field with a sinusoidal distribution in one direction and a homogeneous distribution in the perpendicular direction is analyzed as an example of the chaotic motion. ¿ 1999 American Geophysical Union