The solubility of ethylene in toluene and in toluene (90 wt %)/styrene-butadiene rubber (SBR; 10 wt %) solutions was determined because the solubility data were of interest for the kinetic study of the metallocene-catalyzed homopolymerization of ethylene and the copolymerization of ethylene with alpha-olefins. The data were obtained over the temperature range of 293-343 K and the pressure range of 50-180 psi. An original Universal Functional Group Activity Coefficient (UNIFAC) model was applied for the ethylene-toluene system, and a UNIFAC-ZM model (a modified UNIFAC model proposed by Zhong and Masuoka et al.) was applied for the ethylene-totuene/SBR ternary system. Henry's law was also used to correlate the experimental results of the two systems. A comparison was made between the UNIFAC models and Henry's law. (c) 2005 Wiley Periodicals, Inc.