This text provides an integrated account of Chomsky's ideas about language, based chiefly on the current version of his theory - the government/binding theory of linguistics. It starts from the fundamental concept of universal grammar as a property of the human mind, consisting of universal principles of language and parameters that vary within limits from one language to ather. The implications of this are explored for first language acquisition, concentrating on the contribution of the mind and on the nature of the language evidence necessary. An outline of the sub-theories of GB and their relationship is presented, dealing with topics such as the X-bar theory in syntax, syntactic movement and case theory, with government a pervasive syntactic relationship in the theory. Chomsky's writings of the 1980s are incorporated together with lectures on GB theory, including ideas represented in the Managua and Kyoto lectures.