This paper re-examines the reconstruction of Old Chinese ending *-s as the origin of qusheng (departing tone) in Middle Chinese. Both external evidence and internal evidence for the *-s hypothesis are demonstrated to be insufficient. However, the consistency of external and internal evidence and the comparison between Bai and Chinese suggest that it is more compelling to establish two categories of qusheng words in Old Chinese, one category with *-s ending and the other without *-s ending.