This study determined PP-LFER solute descriptors of neutral PFAS that can be used to predict various partition coefficients. As noted above, many PP-LFER equations in the literature have not been calibrated with PFAS. Extrapolation may reduce prediction accuracy from what could otherwise be achieved. This is not a problem specific to the PP-LFER models. Any empirical model requires high-quality data on PFAS to accurately predict PFAS properties, but such data are often lacking. In our series of studies, we measured Kow, KHxd/w, and KHxd/air for various neutral PFAS, which can also provide Kaw and Koa values via the thermodynamic cycles. Koa, Koil/w, organic carbon/water, and liposome/water partition coefficients can be found in the literature for some FTOHs. Measuring additional partition data for other PFAS or other partition systems would expand the applicability of the PP-LFER approach for PFAS. COSMOtherm, in contrast, is a theoretical model and may have the potential to provide accurate predictions without additional empirical calibration. In the supporting information, COSMOtherm predictions for Kow, Kaw, Koa, KHxd/w, KHxd/air (L), KHxd/w, Koil/w, and Koil/air of 222 neutral (or neutral species of acidic) PFAS are provided for reference (Table ). While reasonable accuracy (within ~1 log unit) is expected as discussed above, further validation of these predictions with experimental data is warranted.