Isothermal vapor-liquid equilibrium data for the binary system of HFC-23 (trifluoromethane, IUPAC) + HFC-134a (1,1,1,2-tetrafluoroethane, IUPAC) were measured at T = (258.15 to 293.15) K in a circulation-type equilibrium apparatus. The experimental results were correlated with the Peng-Robinson-Stryjek-Vera (PRSV) equation of state using the Wong-Sandler mixing rule. The overall average deviation of pressure by the PRSV equation of state was 0.734 %, and the average deviation of vapor-phase composition by the PRSV equation of state was 0.0055.