The need for experts from related disciplines to aid in learning diagnosis and prognosis is discussed. While support for a multi-causation theory of reading disability has been general for many years, it has not led to action, as reflected in the lack of an interdisciplinary approach to learning disabilities in many schools, reading centers, and clinics. Specific diagnostic information must be obtained if appropriate instructional strategies and remedial methods are to be employed. Six levels of diagnosis are suggested, including descriptions of (1) reading performance, (2) behavior affecting reading performance, (3) a detailed analysis of the child's reading process, (4) mental ability, (5) medical problems affecting learning, and (6) family attitudes contributing to learning problems. Examples are given for interdisciplinary areas of evaluation and for the effective use of specialists from other related fields. The experimental interdisciplinary program in Reno, Nevada, is cited. References are included. (WB)