The effect of small addition (0,7 wt.%) of Ge on precipitation during aging at 190degreesC of a modified commercial Al-Cu-Si based alloy has been studied. It was found that the maximum hardness in the alloy containing Ge was achieved three times faster than in the alloy without Ge. TEM results clearly demonstrate that the accelerated precipitation should be ascribed to a dense and fine distribution of Si-Ge particles serving as sites for heterogeneous precipitation of theta" and theta' phases. Accelerated precipitation during aging was accompanied by increase in hardness.