Black South African English, the variety of English used by mother-tongue speakers of South Africa's indigenous languages, has received considerable attention during the last two decades. However, so far most of the accounts of this variety have been only qualitative in nature. This book reports on one of the first studies offering extensive quantitative analyses of four typical features of Black South African English grammar: omission of past tense marking, extended use of the progressive aspect, article omission, and use of left dislocation. Drawing on a corpus of spoken data, the study's focus lies on the investigation of the stability of the selected features and hence aims to ascertain which of these are characteristic of Black South African English as a whole. Speakers exhibiting differing levels of competence in English are compared. It is shown that the analysed features are used by speakers of Black South African English regardless of their proficiency level, but, at the same time, there are considerable differences concerning the frequency of occurrence of these features.