Reliable knowledge of minimum miscibility pressure plays a vital parameter in the design and implementation of any miscible gas injection process and gas-oil interfacial tension extremely impacts on minimum miscibility pressure values. In this article two Iranian oil fields were investigated. Gas-oil interfacial tension technique relies on the measurements of gas/oil interfacial tension by pendant drop at several pressures and reservoir temperature for the first field and results were compared with generated values by the Parachor method. Then at different pressures and constant temperature (115 degrees F) condition in the second field interfacial tension values have been evaluated for different oil-gas molar ratios.