A modified method is discussed that is based on Farooque and Deshpande's method to obtain polymer-polymer interaction parameters using inverse gas chromatography (IGC) data. In the Farooque and Deshpande method, the ratio of the difference of probe-polymer interaction parameters between two polymers and the probe volume [(chi(12) - chi(13))/V-1] is used as the abscissa. In the modified method, the ratio [( phi(2)chi(12) + phi(3)chi(12))/V-1] is used as the abscissa. Experimental data previously reported for a poly(epsilon-caprolactone)-polyepichlorohydrin (PCL/PECH) blend and a poly(ethyl acrylate)-poly(vinyl propionate) (PEA/PVPr) blend are analyzed. It is found that the slopes obtained by the new method had smaller deviations from the theoretical values than the Farooque and Deshpande method. The standard deviations of both slopes and intercepts obtained from the new method are also smaller. Using the new method, the polymer-polymer interaction parameters obtained from the intercept are negative numbers for the PCL/PECH system and very small positive numbers for PEA/PVPr. Explanations are given for the probe and concentration dependency of the polymer-polymer interaction parameters that are generally observed in IGC studies. A new method for selecting the best probe for calculating the interaction parameter is discussed. (C) 2003 Wiley Periodicals, Inc.