The effects of collisional processes on the nonlinear particle dynamics in the magnetotail are considered. A simple collison operator is developed to model the effects of pitch-angle and energy scattering. It is found that the phase space partition persists for up to moderate scattering amplitudes in pitch-angle and energy, and that certain distribution function features are robust even in the presence of large amplitude collisions. It is shown that if the collisions are due to short scale length electrostatic fields, excessively large field ampltiudes are required to significantly alter the phase space structures and the resulting distribution function features. ¿American Geophysical Union 1991