A significant correlation has been shown to exist between the interfacial tension of polymer pairs and their acid-base pair interaction. The relationship is inverse, with interfacial tensions decreasing as acid-base interactions increase. Interfacial tensions, frequently used as an indicator of polymer compatibility, were measured by the breaking thread method at temperatures in the vicinity of 200 degrees C. Acid-base pair interaction values were measured by inverse gas chromatography over wide temperature ranges. The observed correlation confirms the important contribution made by short-range, acid-base interactions to the observed value of interfacial tension and supports the prediction of equations based on fundamental definitions of surface forces. A collateral finding of this work is the decrease of acid-base functionality with rising temperature for all polymers studied.