A multireference configuration interaction (MRCI) approach, based on complete-active-space self-consistent-field (CASSCF) wave functions, with extended basis sets such as Watchers' (14s 11p 6d 3f)/[8s 6p 4d 1f] for nickel and correlation-consistent polarized-valence triple-zeta (cc-pVTZ) for carbon, were employed to revise the lowest-lying singlet and triplet electronic states of NiC. The energetic ordering (T-e values in parenthesis) of the electronic states, X(1)Sigma(+), a(3)Pi (7882 cm(-1)), A(1)Pi (9427 cm(-1)), B(1)Phi (10 156 cm(-1)), b(3)Phi (10 689 cm(-1)), C(3)Sigma(+) (10 835 cm(-1)), C(1)Delta (14 352 cm(-1)), and d(3)Delta (14 363 cm(-1)), was found to be in variance with that obtained previously at the CASSCF level, re-emphasizing the need of including nondynamical and dynamic correlations effects into the wave function of systems containing transition metals. (C) 2003 Elsevier B.V. All rights reserved.