An experimental technique is developed to measure the interfacial tensions of the crude oil + reservoir brine + CO2 systems at pressures from (0.1 to 31.4) MPa and two temperatures (27 and 58) degrees C using the axisymmetric drop shape analysis (ADSA) technique for the pendant drop case. The measured dynamic interfacial tension is gradually reduced to an equilibrium value. For both the reservoir brine + CO2 system and the crude oil + CO2 system, the equilibrium interfacial tension decreases as the pressure increases, whereas it increases as the temperature increases. For the reservoir brine + CO2 system, the interfacial tension data are not available at P >= 12.238 MPa and 58 degrees C because the pendant brine drop cannot be formed in the CO2 phase. However, for the crude oil + CO2 system, the equilibrium interfacial tension remains almost constant at P >= 8.879 MPa and 27 degrees C or at P >= 13.362 MPa and 58 degrees C. Under the same conditions, nevertheless, the equilibrium interfacial tension of the crude oil + reservoir brine + CO2 system is reduced in comparison with that of the crude oil + reservoir brine system. The interfacial tension reduction for the crude oil + reservoir brine + CO2 system is larger at higher pressures.