Class III charges such as CHELPG, MKUFF, and HLYGAT correlate poorly, while Hirshfeld and CM5 charges yield the highest correlations with σm or σp values (R 2 = 0.8-0.9). Another factor influencing the correlation between computed descriptors and experiment is the choice of probe atom: meta-and para-carbon atoms in the aromatic ring produce inferior results to the attached H atoms or other ring substituents. This effect is most pronounced for the prediction of metasubstituent effects, where computed results are the most variable and most methods evaluated at carbon atoms correlate very poorly indeed with σm values. These observations suggest that density-based partition schemes such as Hirshfeld should be generally preferred over basis-set based approaches in obtaining electronic descriptors (such as Hammett parameters) for organic structures, since they are more stable to unphysical perturbations of charge that result from nearby functional groups.