Isothermal (vapour + liquid) equilibrium data were measured for the two systems, (trifluoromethane (HFC-23) + propane) and {trifluoromethane (HFC-23) + n-butane}, at temperatures ranging from 283.15 K to 313.15 K at 10 K intervals. These experiments were performed with a circulating-type apparatus and on-line gas chromatography. Experimental data were well correlated by the Peng-Robinson equation of state using the Wong-Sandler mixing rules and the NRTL model. (C) 2009 Elsevier Ltd. All rights reserved.