Morphologically marked case is a salient Standard Arabic feature without parallel in Arabic dialects. As such it is a grammatical system learned by native speakers of Arabic through formal education. Case endings are traditionally regarded as an essential feature of Standard Arabic, but morphological case endings are used only sporadically in extemporaneous speech in formal situations where Standard Arabic is the expected variety. This study presents a critical discussion of traditional descriptions of the Arabic case system and explores the possibility of there being covert linguistic norms governing where case is and is not marked in formal speech. This is done by quantitatively analyzing televised interviews with Arab politicians for their use of morphologically marked case. The data show that the rate of case marking differs widely between speakers, but also that there are patterns, consistent between speakers, of how case endings are proportionally distributed in various grammatical contexts. The findings presented in this study have important implications for Arabic curriculum development, both in first and second language teaching, and also shed light on the role of the use of case endings in Arabic diglossia.