The staff of the Reading Project of the Learning Research and Development Center at the University of Pittsburgh, having previously experimented with beginning reading programs, adapted commercially available materials for use in an individualized elementary school environment. Their activities culminated in The New Primary Grades Reading System (NRS) designed for the first 3 years of reading instrution. Using a code-breaking approach to the linguistic materials, the program permits individual rates of progress through the 16 levels of the program, each of which contains 10 instructional sequences. NRS stimulates the "real-world reading situation" with such materials as workbooks, story books, games, and cassette-recorded lessons which fall into three categories: (1)"prescriptive"--teacher-controlled, (2) "selection"--limited student choice, and (3) "choice"--greater student freedom. (The four sections of the monograph present the rationale, theory, components, and design of NRS, as well as some examples of the decision-making processes of curriculum designers; a bibliography is also included.) (HS)