xviii, 230 p. : maps. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In this thesis, a reconstruction of Proto-Peba-Yagua is attempted using the comparative method. Peba-Yagua had three members in the past: Yagua, Peba and Yameo. Yagua is the only extant member of the family. Information about the sound inventory and the morphology of the proto-system is provided and discussed based on comparisons of all three varieties. Results show that Proto- Peba-Yagua had at least the consonants *p, *t, *k, *m, *n, *tJ, *R, *h, *w, *j and at least the vowels *a, *e, *i, *u. Peba and Yameo show more similarity with regards to the historical development of their sound inventory. With regards to morphology and grammar, because of lack of evidence for all involved linguistic varieties, the only categories that can be reconstructed are parts of the pronominal system, some classifiers and the locative morpheme *-mV. / Committee in Charge: Dr. Doris Payne, Chair; Dr. Spike Gildea