This study aims to explore the functions and grammatical status of the Kavalan preverbal affix ma-. In addition to agent focus, locative focus, and referential focus (mainly used to focus the instrumental or benefactive case), Kavalan ma- is found to mark specific sentential focus. This marker behaves like agent focus in terms of its grammatical behavior, and is mainly used in two scenarios: spontaneous events, when the event is conceived of as happening spontaneously without an extraneous causer; and anticausatives, when the patient is the focus and the agent is conceived of as insignificant. In some limited cases, ma- is also used for naturally collective/reciprocal events. In ma-marked clauses, the clausal subject is typically conceived of as a spontaneously affected role, and this marker is therefore termed "undergoer focus" in the present study. Similar grammatical devices are found in two other Formosan languages, Paiwan and Amis, both of which share semantic and syntactic similarities with Kavalan ma-. It has been suggested by Evans and Ross (2001) that the same form ma- is commonly found in Oceanic languages, with different functional manifestations cross-linguistically. Further investigation into the manifestations of similar devices in other genetically related languages may help us to gain a better understanding of internal relationships within the Austronesian language family.