Recently, the use of thematic units in the teaching of language arts at the secondary level has significantly increased. This document discusses the theory and practice of using thematic units. The first section provides an overview of the use of thematic units and shows how such units can aid in teaching students about the composing process, literature, the English language, oral communication, and various media forms. The second section presents units for helping students explore the search for identity, the concept of brotherhood, the hero/heroine concept, and past and present roles and goals of women. For each unit, the document provides a course description and suggested achievement level, lists thematic and language arts objectives, suggests materials, and describes a number of learning activities. Section three suggests materials and possible activities for additional units dealing with decision making, death, science fiction, people under pressure, and success and failure. (GW)