This paper discusses three linguistic theories related to communicative competence and English for special purposes in terms of the needs of post-graduate students in Guyarti, India. First, Hymes' theory of communicative competence is understood to be advocating a wider concept of competence than Chomsky's theory. Hymes states that a normal child acquires knowledge of sentences, not only as grammatical but also as appropriate. Secondly, a theory of discourse analysis is examined. It proposes that the organization of concepts is manifested linguistically in connected sets of speech acts. For students to understand linguistic communication, the structures in discourse have to be identified and their functions determined. Third, Widdoson's views on English for Special Purposes focus on the need to devise teaching programs which will develop the ability to handle scientific/technical discourse in English. Widdoson mentions two approaches: the operational, or structural, and the theoretical, or linguistic. Criticism of these methods leads to the conclusion that they presuppose a high level of skill in logical thinking and ability in reading comprehension in English. Where these are lacking, experience has shown that these methods themselves become incomprehensible. (Author/AMH)