The effects of lithium content on the ageing characteristic and notched tensile properties of particulate reinforced Al-Li-Cu-Mg-Zr based metal matrix composites (MMCs) have been investigated. MMC sheet containing 20 wt% silicon carbide particulate produced by a conventional powder metallurgy route aged at a similar rate as unreinforced sheet, and the highest strengths were achieved in samples containing 2-2.5 wt% Li. A proprietary processed 8090 Al-Li alloy MMC sheet aged more rapidly, however, and gave considerably higher strengths, The toughness of Al-Li-Cu-Mg-Zr MMC sheet, as indicated by the notched tensile behaviour, can be improved by reducing the lithium content albeit at the expense of strength.