Theoretical treatment of the subject indicates that the deformation and fracture behavior of fiber reinforced metal-matrix composites depends largely on the strain hardening of the matrix. Experimental results obtained by others on tungsten-reinforced copper (strain hardening) and steel-reinforced Mg-8Li alloy (not strain hardening) confirm this conclusion. It is also shown that fracture depends on the amount and length of the fibers. An upper limit of 30 vol% reinforcement is suggested with short fibers.