SCF and perturbation theory calculations indicate the ground-state equilibrium geometry of HO2NO2 has no symmetry and the plane of the HO2 group is roughly perpendicular to the plane of the NO2 group. CI calculations have been performed for the first five states at the ground-state geometry. These states may be characterized as single excitations on either the NO2 fragment or the HO2 fragment. Comparison with the observed UV photolysis is presented. © 1985 American Chemical Society.