Very few verbs in formosan languages are known to carry a full set of voice affixes, but it remains unclear how and to what extent the lexical meaning of a verb influences constructional variability. In this study we sort out where the gaps may lie, and probe the complex and interwoven nature of the relationships between the semantic roles of nominative arguments and various non-Actor Voice clauses in Tsou. We argue that voice forms are not automatic mechanical processes based on leical selection alone, and we often we insights that show that both lexical and constructional meaning interact in licensing Benefactive Voice (BV) clauses. The argument is also made that two types of BV clauses must be distinguished, causativized and noncausativized. Verbs in noncausativized BV clauses "subcategorize" for nomative NPs that would normally function as "noncore" or peripheral argments in a European language like English, which thus constitutes important evidence that Tsou is a language that does not grammatically make the core/oblique distinction. Causativized BV clauses, on the other hand, have the effect of bringing in an extra argument to the source clauses and marking it with oblique case, while retaiing the case markings on the nominal arguments in the source clauses, violating the well-known causee accessibility hierarchy.