The preparation and characterization of ferrite- and carbon black-filled ethylene-propylene-ethylidene norborene terpolymer rubber composites were studied for microwave applications. Both the insertion loss and return loss were measured in a high-frequency range (X-band) with a network analyzer. The results indicated a relatively low frequency dependence. The difference in the insertion losses measured for all samples, except for one containing 100 phr ferrite and 75 phr carbon black (B75), was +/-3 dB. Sample B75 showed broadband absorption in the aforementioned frequency band. Furthermore, the incorporation of both ferrite and carbon black powder into the rubber matrix altered the electrical and microwave properties, that is, the insertion loss and return loss; this could be helpful in the design of suitable absorbing materials for microwave applications at high frequencies. (C) 2002 John Wiley & Sons, Inc.