Defining schemas as higher order cognitive structures that serve a crucial role in providing an account of how old knowledge interacts with new in perception, language, thought, and memory, this paper offers an analytic account of the nature and functions of schemas in psychological theory and organizes some of the experimental evidence dealing with the operation of schemas in memory. The paper is organized into six sections, the first of which provides a detailed examination of the schema concept as formulated by F. C. Bartlett in 1932. The second section relates Bartlett's theory to the larger issue of the conflict in psychological theory between ideas from British Empiricism and ideas from Continental philosophy. The third section briefly outlines some of the basic theoretical assumptions of information processing psychology to serve as a background for an analysis of schema theory, and the fourth examines modern schema theory, and contrasts it with Bartlett's theory and with the information processing approach. The fifth section discusses the nature of schemas, specifically mentioning ontological assumptions, modularity, ecological validity, and phenomenal experience, while the final section develops a framework for analyzing the functions of schemas in the memory process, and then examines a number of recent experiments in terms of this framework. A 16-page bibliography is included. (FL)