Calculations have been performed on low-lying states of SF6 and SFmath image at the complete active space multiconfiguration self-consistent field (CASMCSCF) level. These calculations involved optimization of basis function exponents, particularly the f-functions on sulfur and their effect on the potential energies and the SF6 electron affinity. The CASMCSCF calculations for the anion and neutral included 4,863 and 2,115 configuration functions, respectively. Octahedral and selected distorted geometries were considered. The ground-state equilibrium geometries correspond to the octahedral configuration of SF6 (1A1g), R(S[BOND]F) = 1.56 Å, ωe = 776 cm−1, and of the anion SFmath image(2A1g), R(S[BOND]F) = 1.70 Å, ωe = 558 cm−1. The adiabatic and vertical electron affinities are found to be -0.63 and 1.8 eV, respectively. Electron autodetachment phenomena associated with the anion are also discussed and a possible mechanism for this process is presented. © 1993 John Wiley & Sons, Inc.