The influence of magnetosphere-ionosphere coupling on the dynamic evolution of the magnetotail is investigated by a three-dimensional resistive MHD code that includes the effects of the closure of field-aligned currents in a simple resistive model ionosphere. Particlar emphasis is on the role of this coupling during substorm evolution and the modification of the latter by the convection driven by the ionospheric electric fields. For comparison, we present results from a simulation which uses an infinitely conducting ionosphere but is otherwise identical. Comparison of the two simulations shows that the major impact of magnetosphere-ionosphere communication is an acceleration of magnetotail evolution. Otherwise, phenomena in the two models are qualtitatively similar. We conclude that ionospheric effects do not significanlty affect substorm associated magnetotail dynamics. ¿American Geophysical Union 1991