The RuC molecule has been a challenging species due to the open-shell nature of Ru resulting in a large number of low-lying electronic states. We have carried out state-of-the-art calculations using the complete active space multiconfiguration self-consistent field followed by multireference configuration interaction methods that included up to 18 million configurations, in conjunction with relativistic effects. We have computed 29 low-lying electronic states of RuC with different spin multiplicities and spatial symmetries with energy separations less than 38000 cm(-1). We find two very closely low-lying electronic states for RuC, viz., (1)Sigma(+) and (3)Delta with the (1)Sigma(+) being stabilized at higher levels of theory. Our computed spectroscopic constants and dipole moments are in good agreement with experiment although we have reported more electronic states than those that have been observed experimentally. Our computations reveal a strongly bound (1)Sigma(+) state with a large dipole moment which is most likely the experimentally observed ground state and an energetically close (3)Delta state with a smaller dipole moment. Overall our computed spectroscopic constants of the excited states with energy separations less than 18000 cm(-1) agree quite well with those of the corresponding observed states. (C) 2004 American Institute of Physics.