Amis (Austronesian, Taiwan) displays a rich, partly symmetrical voice system and a split case-marking pattern which are selected and restricted by (i) verb classes whose basic diathesis correlates with semantic properties such as activities vs. states, and (ii) by Aktionsart features (i.e., atelic activities vs. telic accomplishment and achievements), which also denote degrees of patient affectedness. Referential features such as patient definiteness, and semantic features such as agent's animacy and intentionality also bear on voice selection. This voice system offers alternate ways of encoding arguments within a bipartite case-marking pattern; it also promotes peripheral, non-core arguments to subject function via applicative voice constructions.