We present a comprehensive study of the lattice restricted primitive model, i.e., a lattice gas consisting of an equal number of positively and negatively charged particles interacting via on-site exclusion and a1/rpotential. On the cubic lattice, Monte Carlo simulations show a line of Ne´el points separating a disordered, high-temperature phase from a phase with global antiferromagnetic order. At low temperatures the (high-density) ordered phase coexists with the (low-density) disordered phase. The Ne´el line meets the coexistence curve at a tricritical point,Tt≃0.14,&rgr;t≃0.4.A simple mean-field analysis is in qualitative agreement with simulations. ©2000 American Institute of Physics.