The square-wave voltammetry of isolated isomers of C84 is reported. Based on their relative abundance, the isomers are assumed to have D2 and D2d symmetry. The D2 isomer has four reversible reductions at −0.65, −0.98, −1.34, and −1.75 V versus Fc/Fc+ prior to electrolyte decomposition. This behavior is consistent with previous reports, and is similar to the voltammetry of C60 and C70 (e.g. sequential reductions spaced at slightly increasing intervals). The D2d isomer has five reversible reductions at −0.46, −0.77, −1.58, −1.98, and −2.27 V versus Fc/Fc+ prior to the onset of electrolyte decomposition. The large potential difference separating the second and third reductions of the D2d isomer is an aspect of the voltammetry not reported when the D2d isomer was analyzed as part of a mixture of C84 isomers (P.L. Boulas, M.T. Jones, R.S. Ruoff et al., J. Phys. Chem. 100 (1996) 7573–7579). The large potential difference between the second and third reductions of the D2d isomer of C84 is similar to the voltammetric behavior of C82.