Abstract: Elapsed time of serrations in Al-Li single crystals was investigated with two definitions: one is the time elapsed in one cycle of serrations, the other is the average elapsed time within a strain limit.Elapsed time of individual serration appears independent on stress drops during serrated flow. It primarily distributes within the limits of short elapsed time in peak aged condition compared with underaged and overaged conditions, corresponding to low level of the average elapsed time that appears indifferent to increasing strain. It seems that shearing behaviour of δ' particles could be responsible for the variations in elapsed time of serrations.