The richest verbal system among the rGyalrongic cluster of languages in Tibeto-Burman is found in the Showu dialect of rGyalrong. Drawing on first-hand field data, this paper provides an account of the elaborate morphological patterns in Showu verb-stem formation. Unlike many other rGyalrongic members, Showu possesses non-alternating verbs with invariant stems throughout the paradigm. On the other hand, a good number of basic verbs distinguish a second (or past) stem while many transitive verbs show an additional third (or nonpast singular transitive) stem. Both vocalic, consonantal, and suprasegmental modifications play a role in the formation of the second and third stems. After treating Showu stem variations and their functional distribution, a comparison is made with the more innovative stem-alternating patterns in the Caodeng and Dazang dialects of rGyalrong.