Interfacial tensions of 10 normal alkane + water/brine and hydrocarbon mixture + water/brine systems were measured by using a pendent drop instrument. The temperature and pressure ranges of measurements are (25 to 80) degrees C and (1 to 300) bar, respectively. The effects of temperature, pressure, and salt content have been studied. It was found that the interfacial tension is sensitive to temperature and salt concentration but weakly dependent on pressure and salt species.