Axial fatigue properties were determined on a number of filament reinforced metal matrix composite materials. Results indicated that each of the composite materials possessed excellent fatigue properties when tested parallel with reinforcing filaments (that is, fatigue strengths at 106 cycles of 50 to 80 percent of ultimate tensile strengths). Transverse fatigue properties were found to be similar to those of the unreinforced matrix material. The type and size of filaments and the matrix material and its condition were found to significantly affect fatigue properties. For example, boron-reinforced composites possess higher fatigue strengths than Borsic-reinforced composites at high-stress, low-cycle fatigue, but the reverse is true in the low-stress, high-cycle region; large diameter (5.6-mil) filaments impart superior fatigue properties to composites than do 4.0-mil fila- ments; aluminum matrix composites possess better fatigue properties in the longitudinal direction (that is, parallel with reinforcing filaments), however, titanium matrix composites possess higher fatigue strengths in off-axis directions; disbonds result in lower fatigue strengths; and, heat treatment of the matrix improves transverse fatigue properties but has little or no effect on longitudinal fatigue strength. The fatigue properties of boron 6061 aluminum, Borsic 6061 aluminum, boron stainless steel 6061 aluminum, Borsic stainless steel 6061 aluminum, Borsic titanium 6061 aluminum, and Borsic 6Al-4V titanium are presented and compared to facilitate use by design and materials engineers.