Many methods are available for characterization of elastomer blends, and this work focuses on the microscopical methods that include optical and electron microscopy. The use of electron microscopy, when phase contrast between the elastomers can be obtained, proves to be the most useful technique in terms of being able to characterize both the phase morphology and filler interphase distribution. The factors that control the carbon black-interphase distribution and Me effects of varied phase distribution upon rubber properties in an NR/EPDM sidewall were also examined.