Mg12Li-xAl (x =0, 3, 5) matrix composites reinforced with short 5-alumina fibres were manufactured by the pressure infiltration process. Compression test of cylindrical composite samples were carried out at 20 - 200degreesC. Results obtained revealed the flow stresses increased with an increase in Al alloying and decreasing test temperature. Strain hardening occurred at temperatures below 100degreesC whereas recovery processes were observed at higher temperatures. Different contributions to the strength of the composite were evaluated. The shear stress at fibre/matrix interface seems to be of greatest importance in this regard, though the contribution resulting from the dislocation density increase is also significant.