In this work, great efforts have been made to achieve the large-scale industrial separation of RS-4-vinyl-1-cyclohexene and ZE-3-pentenenitrile. Initially, the vapour pressures of ZE-3-pentenenitrile were determined. The experimental values were correlated by an Antoine-type equation, and the predicted results of vapour pressures showed that the average relative deviation from experimental values was 0.254% for ZE-3-pentenenitrile. Then the isobaric (vapour + liquid) equilibria data of RS-4-vinyl-1-cyclohexene and ZE-3-pentenenitrile were determined at (50.0 and 100.0) kPa. These experimental values were found to be thermodynamically consistent, by means of the point-to-point test and the direct test methods. Two liquid phase activity coefficient models (Wilson and NRTL) were used to correlate the (vapour + liquid) equilibria data of the binary system, and the model parameters were obtained. All models represent the experimental values quite well. The activity coefficients and the reduced excess molar Gibbs energy were calculated by Margules equation, which were found to be in satisfactory agreement with the experimental values. (C) 2015 Elsevier Ltd. All rights reserved.