In critiquing the 1.9 eV error for DFT/CIS, it is worth comparing the performance of conventional TD-DFT as a baseline. Using a functional B x LYP with a variable frac- tion (x) of Hartree-Fock exchange, Besley et al. demonstrated that x = 0.57 performs much better in terms of absolute accuracy as compared to B3LYP with x = 0.20. Mean errors for the B 0.57 LYP functional were reported to be 0.7 eV for core-to-valence transitions of secondrow elements and 0.9 eV for core-to-Rydberg excitations, whereas the corresponding TD-B3LYP errors are 12.7 eV (core → valence) and 12.9 eV (core → Rydberg). Our own benchmarks, using the Quest1 data set, afford a mean absolute error of 0.28 eV for valence excitation energies, essentially identical to the ∼ 0.3 eV accuracy that was reported in the original implementation, using a much smaller data set. This should be compared in context to CIS itself, where average errors are 1 eV. (Keep in mind that there is no XC kernel in the DFT/CIS matrix elements.) Although we plan to provide a more thorough assessment of DFT/CIS for valence excitation energies in due course, preliminary data suggest that this method is no worse than TD-B3LYP, which remains one of the best XC functionals for localized valence excitation energies. At the same time, both DFT/CIS methods significantly outperform TD-B3LYP and TD-CAM-B3LYP for core excitations, as discussed at greater length below.