Al electron ab initio configuration interaction (CI) calculations have been carried out on M(8)C(12) (M = Ti, Zr, V, Nb) and mixed-metal M(4)M’C-4(12) (M = Ti, M)= V, Zr) metallocarbohedrene clusters (met-cars). The structure of a tetracapped tetrahedron of metal atoms with T-d symmetry has been assumed for all clusters. The geometries of the ground state and of certain excited states have been optimized at the open-shell Hartree-Fock or the limited Cf (spin coupling) level of calculation, assuming the constraints of the T-d paint group. Two competing states very close in energy have been characterized for Zr8C12. The probable ground state is a "localized" state with four antiferromagnetically coupled d electrons accommodated in the small tetrahedron of metal atoms. Another low-energy state, with four d electrons "delocalized" on the whole metal framework, was characterized at a slightly different optimal geometry. That state is closely related to the one advocated by Lin and Hall (J. Am. Chem. Sec. 1993, 115, 11165) from orbital energy considerations. After correlation of the 20 metal electrons, the localized state was found to be more stable by 20 kcal . mol(-1). The ground state of all other considered met-cars is unambiguously localized.