In 1986, the National Association of Secondary School Principals, with the assistance of a national task force, published the NASSP Learning Style Profile (LSP) for diagnosis of the cognitive styles, perceptual response tendencies, and instructional preferences of middle level and senior high school students. This monograph offers a short course in the development, theoretical base, and use of the NASSP Profile. Chapter 1, by James W. Keefe, discusses the theoretical basis for development of the profile and describes the research agenda, the working definitions for a multidimensional view of style, the philosophical consensus of the researchers, and the instrument development process. The 24 independent subscales of the profile reflect four higher-order factors: cognitive skills, perceptual responses, study preferences, and instructional preferences. The chapter concludes with implications for practice and a sample profile. Chapter 2, by Charles A. Letteri, discusses how the four factors and the related subscale measures illuminate the various operations and processes of learning. Learning is divided into six information processing phases, each of which is described in detail: perceptual modality, perceptual memory, filter system, short-term memory, working memory, and long-term memory. Chapter 3, by Barbara Ferrell, explores ways that information from the LSP can be used to focus on the learning of individual students, on classroom groups, or on the whole population of the school. Chapter 4, by John M. Jenkins, outlines steps to take in implementing a learning style approach to effective instruction. (TE)