In this paper, the (vapour + liquid) phase equilibrium for the (isobutane + cis-1,3,3,3-tetrafluoropropene) system was measured by the static-analytical method at six temperatures from (303.150 to 353.150) K. The combined standard uncertainties of the temperature, pressure and composition were less than +/- 5 mK, +/- 0.0005 MPa and +/- 0.005, respectively. The experimental results were correlated by means of the Peng-Robison (PR) equation of state (EoS) with Van der Waals (VDW) mixing rule and Huron-Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient model. Good consistency is found by both models. The average absolute relative deviations of pressure are between 0.44% and 0.58% for the PR-VDW model, while the average absolute relative deviations of pressure are between 0.12% and 0.44% for the PR-HV-NRTL model. The average absolute deviations of vapour phase mole fraction lay between 0.007 and 0.008 for the PR-VDW model, while the average absolute deviations of vapour phase mole fraction lay between 0.004 and 0.008 for the PR-HV-NRTL model. The results show that the PR-HV-NRTL model has better performance than that of the PR-VDW model for the binary system. Obviously an azeotropic behaviour can be observed for the system. (C) 2016 Elsevier Ltd.