Or is commonly understood to be a conjunction linking two or more constituents. Ending a sentence with "or" is considered non-canonical in written interaction, but ending a turn with "or" occurs regularly in spoken interaction. This dissertation investigates the interactional work of turn-final or as in "Did his oxygen get low or". In an effort to better understand how interlocutors use such "or's" in naturally occurring everyday interaction, I investigate the sequential environments in which participants employ turn-final "or", the social actions "or"-turns as such accomplish, and the interactional work turn-final "or" accomplishes. My work shows that participants end questioning turns with "or". These questions make relevant confirmation "or" disconfirmation. I found that "or" in turn-final placement relaxes the preference for a confirming response in that both disconfirmation and confirmation can be produced in a preferred manner without dispreferred turn design features. Furthermore, turn-final "or" occurs in environments where there is a knowledge differential between participants. Within such epistemic asymmetries, turn-final or is a resource for interactants to locally work out and index a stance of uncertainty. My work explicates that rather than an error or mistake on the questioner's part, turn-final "or" is employed as an interactional resource that indexes a stance of uncertainty about the produced proposition and that relaxes the preference for a confirming response. As such, this dissertation contributes to the fields of interactional linguistics and conversation analysis in general and to research on grammar in interaction, epistemics in interaction and preference organization in particular. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]