The results of a study of proton and electron acceleration in the Earth's magnetotail are presented. By following the trajectories of thousands of charged particles launched from mantle and tail lobe source regions, distribution functions are calculated at different locations in a model magnetotail. The magnetic field is based on the Tsyganenko [1989> model combined with a constant cross-tail convection electric field. Despite the simplicity of the model and the lack of self-consistent fields, a qualitative picture of the proton/electron plasma sheet emerges including an ion to electron temperature ratio Ti/Te ranging from about 4 to 6 in the magnetotail, in approximate agreement with plasma sheet observations. To explain this result, an analytic expression for Ti/Te is derived based on the particle motion of ions and electrons in a current sheet configuration with a varying normal magnetic field component. The derived expression depends on the ion to electron mass ratio to the one-third power (mi/me)1/3 and a factor that takes the local field gradient into account. Using numerical values from the Tsyganenko [1989> field model in the derived equation gives Ti/Te~5. Another result is that the heated electron distribution functions formed in the plasma sheet are not Maxwellian but instead have power law high-energy tails much like the so-called kappa distributions reported by Christon et al. [1989>. At the edge of the plasma sheet, the calculations show the electron plasma sheet boundary layer extends further towards the lobe than the ion plasma sheet boundary layer, also in agreement with observations [Takahashi and Hones, 1988>. Nonisotropic distribution functions form at different locations in the plasma sheet, including electron beams streaming along field lines just inside the separatrix in the deep magnetotail. Electron distributions that are highly skewed in velocity space are found very near the magnetic null point. The nonisotropic distributions suggest that plasma instabilities and wave-particle interactions could occur in those regions. That such a simple model should reproduce many of the features of the observed plasma sheet indicates that adiabatic and nonadiabatic single-particle motion play important roles in the quiet time magnetotail and suggests that ion and electron plasma sheet formation is a natural consequence of single-particle motion in an X line type magnetotail geometry. ¿ 1998 American Geophysical Union