Magnetic circular dichroism (MCD) and electronic absorption spectroscopies have been used to probe the electronic structure of the classical paramagnetic metal-metal-bonded complexes [Re2X4(PMe3)(4)](+) (X = Cl, Br). A violation of the MCD sum rule is observed that indicates the presence of ground-state contributions to the MCD intensity. The z-polarized delta -> delta* band in the near-IR is formally forbidden in MCD but gains intensity through a combination of ground- and excited-state mechanisms to yield a positive C term.