A novel apparatus, PeDro, for high-pressure measurement of the interfacial tension using the pendant drop method is presented. This apparatus was constructed for accurate measurements in the two- component system of water and compressed carbon dioxide. The main influences on accurate and reproducible results have been investigated, and the results have led to an optimized experimental setup and a quasi-static measuring method. PeDro was calibrated against well-established data for water + air. The experimental error of measurement is smaller than 2%. In this two-phase system measurements were conducted in the ranges (278 to 335) K and (0.1 to 20) MPa. The interfacial tension showed a pronounced dependence on pressure and temperature. A regression function has been found which describes the experimental data in the range investigated with high precision.