Valence SCF/CI calculations using nonrelativistic, relativistic, and semiempirical pseudopotentials have been carried out for the ground states of HBri and HIi (i=+1,0, −1). Autoionization of HBr− and HI− is characterized by the crossing points between the Born–Oppenheimer potential energy curves of the negative and neutral molecules. Relativistic and correlation effects are discussed for several molecular properties. Using semiempirical pseudopotentials+valence-CI, our calculated values for HX and HX+ (X=Br, I) are in good agreement with experiment. The crossing between the 1Σ+ (HX) and 2Σ+(HX−) curves is calculated to occur at 1.70 Å for HBr/HBr− and 1.84 Å for HI/HI−. Dissociative attachment energies for HX/HX− are compared with results from low-energy electron scattering experiments.