Electron paramagnetic resonance spectroscopy has been used to discriminate between the R-and S-forms of the anion radical of camphorquinone. In a chiral solvent [SS- or RR-2,3-dimethoxy-1,4-bis(dimethylamino)butane saturated with sodium iodide], ion association between the semidione and Na+ takes place. PM3 calculations suggest that the complex relationship between the solvent, anion, and cation varies sufficiently with changes in the chiral nature of the solvent or anion radical to alter the appearance of the EPR signal allowing EPR chiral discrimination.