This report is divided into two parts in order to make the practical outcomes of a content referenced interpretive system for standardized reading tests available for immediate use by teachers and others, while presenting the technical aspects of the studies in a form appropriate for study by researchers in the fields of reading and educational measurement. The first part of the report presents a guide to the use of the system, which is designed to enable teachers, librarians, and other media specialists to provide students with instructional materials that are geared to individual reading abilities. The second part is devoted to the technical studies which provide empirical foundations for the system. In its present form, this system enables a raw score from any one of seven widely used standardized reading tests to be interpreted in terms of the probabilities that a student earning that score will be able to read a given book or other instructional materials. Development of the system to this point has been confined to work with students in the fourth, fifth, and sixth grades, and its current use should, therefore, be restricted to these levels. (RB)