The high-pressure phase behavior of polymer-solvent-supercritical carbon dioxide systems was investigated experimentally The polymers used were poly(methyl methacrylate), polystyrene, polybutadiene, and poly(vinyl ethyl ether) at concentrations ranging from 5 to 10% in mixtures with toluene or tetrahydrofuran. The experiments were conducted for temperatures from 25 to 70 degrees C and pressures up to 2200 psia in a high-pressure cell. The effect of the nature of the solvent on the L-LL phase transition was determined. Specifically, interest is focused on the effect of the supercritical carbon dioxide concentration on the mixture phase boundaries.