Kamlet and Taft polarity parameters are presented for three supercritical solutions containing solutes of different polarities at two concentrations. It is shown that the polarizability and hydrogen-bond-donating ability change significantly with pressure. In the lower pressure regime, naphthalene and salicylic acid cause a decrease in the polarity parameters compared with the pure fluid, whereas toluic acid causes an increase. These differences can be explained in terms of solute-solute and solute-indicator clustering. It is shown that there is, however, a direct correlation between the change in the hydrogen-bond-donating ability and polarizability for all solutes and all pressures and concentrations, which is thought to result from changes in the amount of solvent required to solvate the solute.