Expressions are presented, based on equations of state, for the estimation of the solubility parameters of supercritical fluids. These expressions depend on the critical constants and the density of the fluids as well as their acentric factors if not conformal with Lennard-Jones fluids. For those that are conformal an alternative expression depending on the Lennard-Jones parameters is presented. A correlation of solubility parameters of room temperature solvents with the Kamlet-Abboud-Taft solvatochromic dipolarity/polarizability parameters is extended to cover also supercritical fluids. (C) 2005 Elsevier B.V. All rights reserved.