Vapour-liquid equilibrium (VLE) data for seven binary polymer + solvent systems and for one ternary polymer + mixed solvent system have been obtained using the gravimetric-sorption method at 50 degrees C. The binary polymer + solvent mixtures studied include polystyrene (PS), poly(methyl methacrylate) (PMMA) and the random copolymer poly(styrene-co-50% methyl methacrylate) in acetone, methyl acetate and chloroform. Solvent absorption by the copolymer was in between those by PS and PMMA for chloroform, but it was less than those by either homopolymer for acetone and methyl acetate. A modification to the classic gravimetric-sorption technique was established for acquiring sorption data for polymer + mixed solvent systems. VLE data were obtained for polystyrene + chloroform + carbon tetrachloride. A perturbed hard-sphere chain (PHSC) equation of state was used to correlate binary and ternary VLE data.