The electronic states of HBr are discussed. The large number of states observed in the region 8.2 to 10.4 eV (part I) arise by the addition of an electron to the HBr$^+$(X$^2$II$_i$) core. These are `highly excited' states in which molecular orbitals derived from excited atomic orbitals are occupied. Coupling cases similar to those shown in the highly excited states of H$_2$ and of He$_2$ are envisaged, but the situation in HBr is complicated by the orbital angular momentum of the HBr+ ion and by spin-orbit interaction. It is suggested that these coupling cases give rise to the unusual rotational structures observed in some of the absorption bands.