Potential energy curves and spectroscopic constants for 37 low-lying electronic states of Mo-2 and the ground state of Mo-2(+) have been computed using the complete active space multiconfiguration self-consistent field followed by the multireference singles+doubles configuration interaction calculations that included up to 19 million configurations. We compute equilibrium distances (r(e)), vibrational frequencies (omega(e)), and energy separations (T-e). We have suggested tentative assignments for the spectra of Mo-2 including the recent work on resonance Raman and fluorescence spectra of Mo-2. Our work supports the ground state with omega(e) near 450-486 cm(-1), and we suggest that the 394.5 cm(-1) line in the resonance Raman spectrum of Lombardi and co-workers is for the a (3)Sigma(u)(+) state of Mo-2. Our computations are consistent with the recently observed near-infrared spectrum of Mo-2 by Bondybey and co-workers. We have computed a number of spectroscopic systems for Mo-2, which are yet to be observed. Our computed adiabatic ionization energy of Mo-2 is in excellent agreement with Simard and co-workers. We have computed the D-e's of Mo-2(+) and Mo-2.