The purpose of this dissertation is to determine whether Sheng, a language spoken in the Eastlands area of Nairobi, Kenya, is a mixed language (incorporating Swahili, English and local vernaculars). The study focuses on the lexicon and morphosyntax, but social factors are examined as well. Three broad research questions are addressed: (1) Does Sheng have a core vocabulary separate from that of Swahili? (2) How do the system morphemes of Sheng compare with those of Swahili? And (3) in what manner does Sheng provide its speakers a new identity?With respect to question one, the core lexicon, like Russenorsk's, Trio-Ndjuka's and Michif's, manifests a nearly fifty-fifty split in Sheng (52% Swahili; 48% other), making it a mixed language lexically.As for question two, the analysis reveals that Sheng has a composite morphosyntax. No object or relative affixes are marked on the verb. Predicate-argument structure from English has provided a null relativizer. The aerial feature imperfective suffix -a(n)g- is preferred 68% of the time. Noun classes show convergence leveling. The marker ma- serves as the generic plural. The diminutive markers, (ka-, to-), constitute a complete non-Swahili subsystem. Consequently, Sheng is also a mixed language morphosyntactically.In reference to question three, a negative correlation exists between competence in Sheng and income and housing. Though the affluent display a negative attitude towardSheng, they agree with the lower socio-economic groups that Sheng has a communicative utility in metropolitan Kenya. A comparison of the usage in the different residential areas establishes that community-wide grammatical norms (i. e., stability) exist in Sheng. Over two decades without institutional support for Swahili provided a niche in which Sheng, a non-standard language variety, flourished and a new urban identity emerged.Eastlanders walk a linguistic tightrope, balancing between the labels mshamba (`rube') and Mswahili (`slick talker'). However, Sheng provides a sociolinguistic embodiment symbolizing what nuances their existence. Over time, speakers formed a new identity group, whose language was initially `off target' (1899-1963) but subsequently became deliberate postcolonially. Finally, the name of the language itself (Sheng < LiSheng < lish-eng < English) results from and is symbolic of this social transformation. / Department of English