[en] For equilateral triangle geometries (point group D/sub 3h/), the C₃H₃ radical has a degenerate ²E'' electronic ground state. Although the ²A₂ and ²B₁ components separate in energy for C/sub 2v/ geometries, these two components should have identical energies for equilateral triangle structures. In fact, when approximate wave functions are used and the orbitals not required to transform according to the D/sub 3h/ irreducible representations, an energy separation between the ²A₂ and ²B₁ components is observed. At the single configuration self-consistent field (SCF) level of theory this separation is 2.8 kcal with a double-zeta basis set and 2.4 kcal with double-zeta plus polarization. It has been demonstrated that this spurious separation may be greatly reduced using multiconfiguration self-consistent field (up to 7474 variationally optimum configurations) and configuration interaction (up to 60 685 space and spin adapted configurations) techniques. Configurations differing by three and four electrons from the Hartree--Fock reference function are found necessary to reduce the ²A₂-²B₁ separation to below 0.5 kcal