Contact discontinuities in a collisionless plasma are studied by hybrid simulations, in which ions are treated as particles and electrons are considered as a fluid. It is demonstrated that contact discontinuity with a stable density ramp can exist in cases with a finite electron temperature. An electron pressure gradient is present across the contact discontinuity, leading to the presence of a parallel electric field and hence field-aligned potential increase (Δ&PHgr;∥) in the transition region. By reflecting ions at the discontinuity, this parellel electric potential peak reduces the interpenetration between hot and cold ions and maintains a stable density ramp across the contact discontinuity. The ratio of the field-aligned electric potential energy to ion thermal energy, eΔ&PHgr;∥/kTi, is found to be an increasing function of Te/Ti, where Te and Ti are respectively the electron and ion temperature. ¿ American Geophysical Union 1994