The application of supercritical fluids to catalytic hydrogenation reactions is studied, on the basis of phase equilibrium predictions by a group contribution with association equation of state (GCA-EOS). Two hydrogenation processes are analyzed: the hydrogenation of triglycerides (TAGs) and that of fatty acid methyl esters (FAME). New binary parameters are given for the interaction between H-2 and the remaining functional groups present in the reaction mixtures. The agreement between the GCA-EOS phase equilibrium predictions and the few experimental data available in the literature for this type of systems is discussed. The GCA-EOS is an adequate toot to find feasible operating conditions for a homogeneous supercritical hydrogenation.