The age-hardening behaviour of Al-Cr alloys containing varying amounts of chromium has been studied, and the effect of silicon on the ageing response of the alloy system was also investigated. Hardness measurement and tensile properties evaluation were used to describe the ageing response of the alloys. With the aid of microstructural observation, the ageing mechanism has been explained. Results of isothermal ageing were used to describe the kinetics of precipitation in both the binary and ternary alloys. It was noticed that the age hardening in aluminium-chromium alloys was mainly due to the precipitation of intermetallics on to the dislocations. The ageing response of the binary alloy containing chromium in excess of its solubility limit was rather poor. However, addition of silicon helped to improve the ageing response of the alloys. Silicon was found to stimulate nucleation of ageing precipitates in the investigated alloys.