A collection of papers delivered during the Fifteenth Annual International Reading Association Convention is presented which represents a variety of views on diagnosis and/or on the manner in which diagnistic information is interpreted. The papers have been arranged into three sections. The first deals with the importance of diagnosis, presents some methods for collecting and interpreting data about reading progress, and describes a plan for bringing about changes in reading performance. The second section treats tests and testing and provides information on ways a teacher can use tests. Included are an analysis of several diagnostic tests currently available, a discussion of problems and solutions in utilizing both standardized and informal tests, and a description of the development of a diagnostic test. Section 3 is composed of four reports analyzing data to shed light on the relation between intelligence and reading improvement, the stability of reading achievement, and critical evaluations of methods for determining levels of achievement. The papers are arranged in a way that makes the monograph easy to use, especially the treatment of the statistical studies. Tables and references are included. (This document previously announced as ED 047 909.) (Author/DH)