This article considers the issue of the application of linguistic theory and knowledge about the way language functions to second language teaching. It is suggested that this application should be carried out by taking into account educational factors, such as the intended audience, the teaching methods, and the educational objectives. The choice of the particular linguistic description used will be determined by these factors. In terms of the intended audience, for example, the learner's native language should be taken into account, as well as level of education, age, and level of linguistic knowledge. Other such factors are discussed, and three instructional goals are listed: (1) the acquisition of communicative competence, (2) the acquisition of descriptive ability, and (3) the acquisition of basic knowledge of the language. The optimal situation combines all three of these goals. Application of this framework to a course in English as a second language is described, with particular emphasis on the teaching of intonation. (CLK)