This paper describes the arguments made for using interdisciplinary approaches in school curriculum. Specifically examined are the historical antecedents that inform discussions of interdisciplinary studies; how interdisciplinary studies are organized; whether differences exist across content areas; general assumptions made about teaching and learning; and how interdisciplinary studies are presumed to improve upon traditional approaches to school curriculum. The review focuses on frameworks, justifications, and reasons that may be built partly on empirical evidence and also on assumptions about teaching and learning not easily reduced to empirical facts. An extensive ERIC search was conducted. Following examination of these initial 150 documents, other relevant resources and bibliographies were examined. Additionally, an analysis of curriculum standards published by professional teaching organizations determined if justifications for interdisciplinary studies were provided in these documents. Coordinating disciplines has been a primary feature of curriculum planning since the turn of the century, but is seldom seen in modern schooling. Recently, however, research in cognition and projected demands from the 21st-century workplace have brought pressures for a more connected vision of the curriculum. Both brain response and higher-order thinking tasks were found to demand authentic, complex, multiple, and concrete problem-solving experiences. Many terms are used in the literature--core, interdisciplinary, fusion, integrated, cross-disciplinary, correlated, integrative, and trans-disciplinary. Three representations stand out: interdisciplinary, integrated, and integrative. All three approaches attempt to connect the student with the abstract world of disciplinary knowledge and the real world of experience. (Includes two tables of models; contains 124 references.) (NKA)