A new simulation model of the thermosphere, the ionosphere, and the magnetosphere is presented. This model, which we call the magnetosphere-thermosphere-ionosphere electrodynamics general circulation model (MTIE-GCM), calculates the three-dimensional structure of the thermosphere and the ionosphere, the two-dimensional magnetospheric plasma convection in the equatorial plane of the magnetosphere, and the couplings among the thermosphere, the ionosphere, and the magnetosphere. The electrodynamic couplings induced by the auroral precipitation, the region 2 field-aligned currents, and the neutral winds are self-consistently computed. The major drawback of the model is the use of a dipole magnetic field in the magnetosphere such that we do not expect to reproduce observations exactly but rather to predict only correct orders of magnitude. The MTIE-GCM is run for solar maximum conditions and moderate magnetic activity in a sample case, where the electric potential is imposed in the polar cap but calculated everywhere else, to study the electrodynamic couplings occurring at high latitudes. The neutral winds increase the north-south component and decrease the east-west component of the ionospheric electric field, corresponding to an enhancement of the shielding effect by 10%. The region 2 field-aligned currents and the distribution of the magnetospheric pressure present smaller modifications, suggesting that the magnetosphere acts partly as a current generator. However, the results could possibly be different if the polar cap electric potential were allowed to change due to the neutral winds. ¿ 1998 American Geophysical Union