English for special purposes (ESP) is the fastest growing facet of language teaching, led by the efforts of British and American linguists. The learner-centered orientation in English-as-a-second-language instruction and the expressed need of people around the world have stimulated development in the field. ESP courses are generally either occupational or educational in emphasis, and are either offered independently or integrated with content areas. Four elements are recognized as essential to ESP courses: needs assessment, materials development, teacher preparation, and evaluation. ESP research, particularly concerning the language of science and technology, has developed four basic emphases: traditional attitudes to the language of science, linguistic analysis of the lexicon, linguistic analysis of syntax, and discourse analysis. While no single model exists for the development of instructional materials because of the diversity of needs and program objectives, general elementary programs teaching English in a science context have been created and some other materials have found widespread use. There have been a variety of approaches to ESP course design, but the elements that need development are a finite structural approach for program sequencing and a strong theoretically-based curriculum design model for materials development oriented to client needs. Thirty-three references are included. (MSE)