Special education professionals in Illinois were surveyed regarding case study procedures for use with mentally retarded students, rating usefulness of procedure, modifications desired for use with different age groups and severity of retardation, and what professional should hold primary responsibility for component completion. Processes rated include child interview, parent consultation, adaptive and cultural social development studies, medical histories, vision and hearing screenings, academic history, learning environment assessment, and specialized evaluations in several therapeutic fields. Psychoeducational and medical components were generally considered more useful than social/environmental ones. A substantial reliance on specialists for assessment was observed, while both administrators and special educators were generally not considered especially important to diagnostic teams in case study work. Five references. (PB)