This paper presents a part of the continuing work toward a better modeling technique for the deformation of metal-matrix composites (MMCs) during mechanical deformation processing. The elastic/plastic behavior of partially aligned short-fiber composites loaded in the principal directions has been studied by using the generalized Eshelby inclusion method and incorporating the mean field theory. The plastic deformation of the matrix material is approximated by using the secant moduli for monotonic, proportional loading. Through a volume average procedure the basic formulation is found similar to that of a simple orientation average on the Eshelby tensor. The calculated Young's moduli are close to the lower bound for composites containing less aligned fibers. The influences of the distribution of fiber orientation on the plastic behavior of composites and the internal stress in fibers oriented at a particular angle are also studied. A case study of the extrusion of MMCs was conducted to obtain an insight into the fundamental behavior.