Accurate thermochemical and spectroscopic properties have been calculated for the X∼2A″ and A∼2A′ electronic states of the HS 2 radical using highly correlated coupled cluster methods with explicit basis set extrapolations. The heat of formation of HS 2 at 0K is predicted to be 26.1kcal/mol based in part on accurate benchmark calculations of SH and S 2 . The equilibrium geometry of HS 2 , which is estimated to be accurate to at least 0.002Å, is predicted to be r e (SH)=1.3482Å, R e (SS)=1.9608Å, and θ e (HSS)=101.52°. In addition to a set of centrifugal distortion constants, harmonic frequencies, and vibration–rotation coupling constants being calculated for both electronic states of HS 2 and DS 2 using second order perturbation theory, the anharmonic infrared band origins and A∼–X∼ emission spectra were calculated variationally together with their intensities. These made use of accurate three-dimensional, near-equilibrium potential energy and dipole moment functions. The ν 3 fundamentals of both HS 2 and DS 2 are reproduced to better than 3cm −1 . Predictions are made for both the ground state infrared spectrum as well as the electronic spectrum. Two possible misassignments in the recently reported chemiluminescence spectra are noted.