Solubilities of monomer gases in polymer solutions are essential data for developing polymerization processes. In this work, the solubilities of ethylene in cyclic olefin copolymer (COC) solutions including toluene and norbornene which are related to production of COC were investigated. The solubilities of ethylene in toluene + COC and in norbornene + toluene + COC solutions were measured at temperatures of 323 K, 343 K, and 363 K and at pressures up to 5 MPa with a synthetic method. The Sanchez-Lacombe equation of state was applied to the data and it was found that bubble point pressures of the quaternary system could be correlated to within 1.5% with binary interaction parameters. (C) 2013 Elsevier B.V. All rights reserved.