This thesis looks at the negation system of the Cairene Arabic dialect, in which the two main negation markers are miš and ma—š. Their main distribution is as following: ma—š is used for negation of verbal predicates except for the ḥa–imperfect, which indicates future tense, as well as quasi–verbs in terms of prepositional phrases when they are inverted predicates. miš is used for nominal negation, the ḥa–imperfect and quasi–verbs in terms of active participles. For bi–imperfect verbs people tend to use both negation markers. In addition to these core rules, studies show that the negation markers can change places in order to express specific pragmatic functions. New observations have been made of non–standard usage of the negation marker miš, where it contradicts traditional rules in Cairene Arabic. In these observations, miš is used for negation of y–imperfect and perfect verbs as well as prepositional phrases. This usage appears to be common in the neighbouring Šarʾiyya district, but, at least traditionally, not in Cairo. This thesis investigates whether there is a change in progress in distribution of the negation markers in the Cairene dialect, or whether the non–standard practices are cases of different pragmatic functions for the negation markers. The study shows that non–standard usage of miš has become a more frequent phenomenon in recent times. However, it does appear to be restricted to certain speech groups and contexts, and does not seem to be widely accepted by speakers of the Cairene dialect. Whether this linguistic phenomenon will spread, become widely accepted and constitute a change in progress in the Cairene dialect, will be interesting to observe in the future.