There is now an increasing body of evidence which suggests that the onset of a substorm expansive phase is triggered in the near-Earth tail region, inside X~-12RE [Samson et al., 1992>. For this reason, it is necessary to characterize the magnetic field in the near-Earth region, particularly the quiet time reference field. We have therefore carried out a detailed study of the magnetic field at geostationary orbit, using data acquired during quiet times from the GOES 5 and GOES 6 satellites which operated simultaneously during 1986. Diurnal and seasonal variations of the total field, and the perturbation magnetic field with the IGRF removed, have been identified and attributed to variations in the position of the neutral sheet with respect to the satellite. We have processed the data to remove seasonal effects by using the semiempirical expression developed by Lopez [1990> to express the displacement of the neutral sheet with respect to the magnetic equatorial plane. We then use our magnetic field model, recently developed by Donovan [1993a>, to model the observed quiet time magnetic field at geostationary orbit, and also determine the quiet time current configuration. ¿ American Geophysical Union 1995