Abstract: Serrated flow has been investigated in binary Al-Li single crystals treated from as-quenched to overaged conditions. Serrations were observed during the deformation of crystaIs aged from 10to 100 h at 448 K. but not in the as-quenched and naturally aged conditions. The number of stress drops for serrations persistently increases within small stress drop limits as ageing time increases until attainment of peak-aged condition. Crystal orientations have some effects on stress drops for serrations.