The aim of this work is to show a computational tool capable of carrying out isothermal two-phase PT-flash using a multicomponent approach. PVTpetro consists of a compositional PVT simulator and it was developed to predict phase behavior and thermodynamic properties of hydrocarbon mixtures. One of the modules of this program is two-phase PT-flash, used for oil and gas systems. This is based on the modelling of vapor-liquid equilibria using cubic equations of state (EoS). Rachford-Rice equation was implemented, allowing the quantity and composition of each existing phase to be determined, whereas, for compressibility factor and fugacity of distributed components in each phase, SRK and PR EoS were applied. Results were compared to commercial simulators, so that the generated responses presented similar results.