Digital computer calculations in SCF MO approximation on the two lowest excited states of BH, 1σ22σ23σ4σ, 3Σ+ and 1Σ+, from 2.0 a.u. out to dissociation are reported. As shown previously by Grimaldi and coworkers , these are stable Rydberg states, but it is now shown that the 3Σ+ potential curve on increasing the interatomic distance R goes over a maximum and then becomes a repulsion curve dissociating to normal atoms. The changing characteristics of the 2σ, 3σ and 4σ orbitals as a function of R are described and discussed. Copyright © 1971 John Wiley & Sons, Inc.