The effect of supercritical carbon dioxide (scCO(2)) on the interfacial tension between a polymer melt pair-polystyrene (PS) and low density polyethylene (LDPE)was studied using the pendant drop method at temperatures varying from 200 to 240degreesC and CO2 pressures up to 18 MPa. The LDPE melt was prepared in a high pressure optical cell and the PS pendant drop was injected into the LDPE melt with a special high pressure syringe. For measurements with scCO(2), the optical cell was first pressurized with scCO(2) and measurements were taken after the saturation of scCO(2) into both polymer melts. Excellent agreement was found with literature data for the same system without using scCO(2). For the polymer pair saturated with scCO(2), it was found that the interfacial tension decreases significantly with increasing CO2 pressure and appears to level off at higher CO2 pressures.