The toughness of PP/EPDM blends was measured over a wide range of temperature (25-132 degrees C) and composition (0-26 wt% EPDM). It was found that increasing temperature and decreasing interparticle distance have equivalent effects on the brittle-tough transition of toughening PP with EPDM, and the shift factor increases with increasing temperature. A correlation was also found between temperature and critical interparticle distance. When critical interparticle distance was plotted versus T-g-T, where T-g is defined as the brittle-tough transition temperature of the matrix itself, the curves for different blend systems converge to a single master curve.