Proper constitutive equations and transformation laws to describe short-fiber-reinforced composites have been reviewed. The mechanisms of load transfer between matrix and fibers have been presented. Micromechanics analyses were discussed in order to predict mechanical properties of the composite given those of the constituents. Such approaches have been used successfully for cord-rubber and particulate-filled elastomeric composites. The use of such methods for short-fiber reinforcement has been limited so far. The problem is more complex in this case, but the need for a reliable method is even stronger in order to evaluate the influence of a parameter change on the various mechanical properties. Elastomeric composites pose a greater change due to the large ratio of fiber-to-matrix moduli, and predictions may not always be accurate. However, the interest of micromechanics approaches is that they allow determination of the effect of a perturbation in the parameters about a given level. Areas for future work include the development of micromechanics methods to determine viscoelastic constants and strength under various loading conditions. The development of a multiaxial strength criterion is needed, and basic fatigue failure mechanisms have to be studied.