The question of register in Arabic is often framed in terms of a so-called “problem of diglossia:” an unstable language situation that will be resolved by the classical or formal registers and the spoken or colloquial ones coming closer together or even merging. This paper argues that the register situation in Arabic might be more stable than previously believed, as speaker behavior helps maintain these registers. In previous work, I showed that native speakers use “avoidance strategies” in writing to maintain the register divide between colloquial and formal registers. In this study, I claim that case-endings are used by speakers to negotiate language register and personal style in ways that are universally understood, and these functions are fundamental in maintaining case-marked speech as an important register of Arabic. While case-marking is prescriptively obligatory in formal registers of Arabic, it is used only sporadically in modern spoken contexts, even in formal environments, where it is understood to be more or less superfluous to communication and functions only to indicate the highest degree of formality possible. This study takes a more nuanced view of how case-marking is used, arguing that it functions semantically, pragmatically, and socio-linguistically. The paper first presents evidence of two different kinds of case-ending usage: one involving not only syntax but also semantics and pragmatics, and another which has no role in any of those areas, but which instead acts to raises or lowers the linguistic level or register of speech. The study then investigates how speakers make use of the latter type of non-semantic case-marking as an integral part of their rhetorical strategies and to negotiate and maintain the linguistic level of their conversation. The study also shows that individuals make conscious and systematic use of case-marking to present a style that is personal but nonetheless draws on shared social and linguistic norms. The paper concludes that the extra-syntactic roles of case-marking have contributed to its survival, and prevented it from simply disappearing as many commentators have predicted. The study is based on quantitatively and qualitatively analyzed evidence drawn from publicly televised speeches, debates and interviews, with male and female speakers from across the Middle East.