This thesis is concerned with the dialects of Hausa as spoken in Nigeria. There are five chapters and three appendices. The first chapter is composed of two parts. The initial part discusses two things, namely (i) the genitic affinity of Hausa and its status within West African languages, (ii) the various contributions made to the study of Hausa, in particular those which are either directly or indirectly connected with dialect variation. The second half of the first chapter examines different approaches to dialect study, such as the traditional approach, the structural approach and the generative approach. Of these, the generative approach is preferred, hence it is the method adopted here to account for Hausa dialect variation. Chapter two aims at presenting in an overall way the major differences that exist between the dialects. The presentation is along traditional lines. Here the dialects of Hausa have been classified into two major dialects, namely East-Hausa and West-Hausa. The criteria for this classification are the phonological and morphological isoglosses. A lexicostatistic analysis carried out during this survey supports this classification. Chapter three concerns the general phonology and phonetics of Hausa. The points discussed here are basically the systematic segments and the distinctive features. Chapter four concerns aspects of the morphology. Here we account (by means of various rules) for the morphological differences between the dialects as seen in Chapter two. The entire analysis is within the theory of generative phonology as developed by Chomsky and Halle (1968). Chapter five discusses the various phonological rules operating in both dialects with regard to the types of mechanisms involved in dialect differentiation. Here it has been observed that rule addition, rule simplification and rule loss are the prime agents in our dialect variation, while differential rule ordering is not. There are three appendices, (i) a brief discussion of syntax, (ii) a discussion of the unsystematic nature of vowel correspondences between Hausa dialects, (iii) the word list employed for lexico-statistic calculations, together with relevant notes on its composition.