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The pendent drop or standing bubble method is applied to measure the interfacial tensions between water and nonpolar fluids (n-hexane, n-heptane, nitrogen, oxygen and methane)up to 473K and 220MPa. The high pressure autoclave with t wo visual windows and the auxiliary equipment are described. The sizes(ca 2mm) and shapes of drops or bubbles are recorded with microscope and video camera. The use of digital image permits fast, precise determination of the contour parameters. The densit y values of the liquids or gases have been chosen from literature.A special program is proposed to calculate the interfacial tensions automatically from drop shape at given temperature and pressure. The interfacial tensions σ12 increase with pr essure for the twoliquid-liquid systems,but decrease with pressure for the three gas-liquid systems.