This chapter provides an overview of PSIs (polarity-sensitive items) in Arabic and briefly outlines the critical issues in the syntax of PSIs in Arabic and their contributions to Arabic syntax and linguistic theory. It also outlines the theoretical underpinnings of research on Arabic negation, relying on the author’s most recent publications. The author synthesizes the major and crucial findings from cross-linguistic studies on this topic and studies of PSIs in Arabic. This chapter also articulates the critical issues, methodology, and scope of content. A quick overview of polarity sensitivity reveals much of the microvariation in Arabic. Geographically, this variation comparatively grows at the phonetic, morphological, and lexical levels, moving from the west with the Moroccan dialect, into Egyptian and Jordanian along the Mediterranean, into the Arabian Peninsula with Qatari Arabic, and into the formal written Arabic.