This dissertation introduces the language situation and discusses phonology (synchronic and historical) and morphosyntax (word order, word classes, the verb complex, aspect, case marking, nominalization, question formation, relative clauses and other essential aspects of Dupaningan grammar). Dupaningan Agta has a relatively simple phonological system, with fifteen consonants and five vowels. Of note, *a has been fronted to /i/ or /e/ after the voiced stops /b d g/. Morphosyntactically, the language has a typical Philippine-type “symmetrical voice” or “focus” system. The voice system of Dupaningan Agta is explored. Finally, this dissertation includes a substantial vocabulary and selection of texts.