Accurate potential energy curves, dissociation energies and molecular constants for several low-lying singlet and triplet electronic states of MgS were investigated using the CASSCF/MRCI methodology, and the cc-pVQZ basis set. Our results represent an improvement over previous theoretical description for the lowest lying states, characterize some higher excited states not previously investigated, and also confirm the assignment of the B-1 Sigma(+) excited state investigated experimentally. Transition probabilities and radiative lifetimes were also predicted using Einstein spontaneous emission coefficients. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.