This paper presents the morphophonological effects of four suffixes on noun stem vowels in Kumzari: thesimple plural suffix -an, the existential plural clitic -in, the definite suffix -ō, and the indefinite suffix -ē.Two of the suffixes (-an and -ō) have an effect on the stress placement of their host stem. This results inan array of alternations which may be generalized as lengthening of the stem’s final vowel and, in the caseof -ō, harmonization of the stem’s final vowel to that of the suffix. The remaining two suffixes (the clitic-in and the suffix -ē) are included in this study to emphasize the role of stress placement in vowel alternationsin Kumzari: although -in and -ē are segmentally and semantically analogous to the first two suffixes– and, in the case of -ē, morphosyntactically equivalent – they have no effect on stress placement and consequentlydo not precipitate vowel lengthening or harmonization.