Serrated flow in as-quenched and aged Al-8.4 at.% Li alloys has been investigated between 253 K and 353 K at strain rates ranging from 8.9 x 10(-5) s(-1) to 1.2 x 10(-2) s(-1). Size and volume fraction of delta' precipitates were determined by small angle scattering and transmission electron microscopy. Growth and coarsening of the precipitates induces different trends of critical strain of serrated flow changing with temperature and strain rate. The stress drop of serrations increases to some extent with increasing ageing time, increasing deformation temperature and decreasing strain rate. The volume fraction of delta' precipitates decreases as deformation proceeds. The characteristics of serrated flow are related to the changes in microstructures during deformation.