This dissertation examines floating tones and tone gesture deactivation in Sierra Juarez Zapotec (SJZ), and provides an Optimality Theoretic account of tonal spreading and placement using insights from Articulatory Phonology. While the data portion of the dissertation is drawn from SJZ, the approach has broader implications for theories of tonal representation and analysis. Constraints that prohibit tone deactivation except in specific locations such as at an utterance boundary, at a following anti-phase coupled tone, or with the vowel of a stressed syllable are proposed. Constraints that reference the coupling point (onset) of a tone are proposed which can draw a tone gesture to couple to a prominent position such as the initial syllable. Constraints are also proposed which prohibit the overlap of activation of tone gestures with other vowel or consonant gestures. In this way, the dissertation proposes that both the onset and endpoint of a tone may be controlled via constraints in the grammar. Fieldwork by the author is presented which illustrates that in SJZ the first-person singular form of transitive verbs has a high tone that does not appear on the first-person singular suffix. Instead, this high tone appears on the stressed syllable of the verb root, and, in cases where the aspect marker is toneless, on the aspect marker as well as the stressed syllable of the verb root. Because the tone appears in locations separate from the first-person singular suffix, it is called a floating tone. The constraints proposed in the dissertation account for the placement of this floating tone while making testable predictions for other languages. The proposed constraints suggest that tone spreading should normally be rightward due to the unique deactivation properties that tone gestures possess (as distinct from consonant or vowel gestures). Leftward spreading is predicted to occur only when a tone is drawn to couple to a prominent position such as with the vowel of the initial syllable. In cases where a tone changes its coupling (onset) and then spreads rightward, the output pattern will appear to be bidirectional. In cases where the onset of a tone does not move, spreading is predicted to be rightward until the tone encounters a deactivator. The predictions made by the constraints are tested via OT analyses of other languages. Several areas where these constraints could be applied in future research are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]