The article focuses on short-rooted infixed and sta stem verbs attested in the works written by Samogitian authors dating back to the 16–19th century. In this article the aforementioned verbs are classified and analysed according to the type of the consonant closing the verbal root which supposedly underpins different models of their constructional alternation. The morphological structure of verbs attested in the old Samogitian scripts exhibit similar alternation models to those found in current Samogitian sub-dialects, however, there are some notable differences as well. The verbs found in old Samogitian scripts are compared to those found in Samogitian sub-dialects in order to determine the localization of alternating forms, their chronological and areal distribution as well as the tendencies and motives for their structural change. Also, an attempt is made to determine the earliest stage and localization of the use of na stem forms attested in the Samogitian written texts in question.