The finite element method is applied to stress and strain analyses around rigid spherical particles in elastomers at large extensions. The stress and strain distribution computed agree well with the classical theoretical ones at small strain. At large extension, however, the maximum stress concentration factor increases greatly and the maximum strain concentration factor decreases slightly as strain increases. These tendencies are increased more in carbon black-filled elastomers than in unfilled ones, which can be understood reasonably by considering both the geometric and material non-linearity. Reinforcement of elastomers with rigid spherical particles was also analysed through a numerical computation. The computed results agree with the Guth and Mooney equations at low volume fraction of fillers. In carbon black-filled elastomers, on the other hand, where the modulus is much higher than that given by the above equations, the computations give a good agreement with the experiments, considering the 20% increase in effective diameter of the filler.