In this paper, an attempt is first made to clarify and tease apart the somewhat confusing terms genre, register, text type, domain, sublanguage, and style. The use of these terms by various linguists and literary theorists working under different traditions or orientations will be examined and a possible way of synthesising their insights will be proposed and illustrated with reference to the disparate categories used to classify texts in various existing computer corpora. With this terminological problem resolved, a personal project which involved giving each of the 4,124 British National Corpus (BNC, version 1) files a descriptive "genre" label will then be described. The result of this work, a spreadsheet/database (the "BNC Index") containing genre labels and other types of information about the BNC texts will then be described and its usefulness shown. It is envisaged that this resource will allow linguists, language teachers, and other users to easily navigate through or scan the huge BNC jungle more easily, to quickly ascertain what is there (and how much) and to make informed selections from the mass of texts available. It should also greatly facilitate genre-based research (e.g., EAP, ESP, discourse analysis, lexicogrammatical, and collocational studies) and focus everyday classroom concordancing activities by making it easy for people to restrict their searches to highly specified sub-sets of the BNC using PC-based concordancers such as WordSmith, MonoConc, or the Web-based BNCWeb.