Potential energy curves and spectroscopic constants for 30 electronic states of Mo-2(+) together with the ground states of Mo-2(-) anion and Mo-2 have been computed using the complete active space multiconfiguration self-consistent field (CASMCSCF) followed by the multireference singles + doubles configuration interaction (MRSDCI) calculations that included up to 44.4 million configurations. We have reported computed equilibrium distances (r(e)), vibrational frequencies (omega(e)) and energy separations (T-e). We have predicted several spectroscopic systems for Nlo', which are yet to be observed and the electron affinity of Mo-2. (C) 2002 Published by Elsevier Science B.V.