A numerical method to iteratively approach three-dimensional magnetostatic force equilibria is presented. The emphasis of the modeling is on the development of a suitable model of the Earth's magnetotail, including a portion of the inner magnetosphere, i.e., on models which violate the ''tail approximation'' commonly employed in analytical models. The numerical approach will be discussed and compared to methods developed for laboratory plasma physics. The method is then applied, as a first example, to the magnetotail outside of 10 RE using Tsyganenko's (1987) model for the quiet magnetosphere as an initial condition. We discuss the changes of the magnetic field necessary to yield an equilibrium configuration and the resulting distribution of the self-consistently derived pressure. At last we will show that a self-consistent magnetotail equilibrium based on a close approximation to Tsyganenko's model requires a region 1 type current system which is not present in the initial configuration. ¿ American Geophysical Union 1993