The dominant instructional model within special education, Differential Diagnosis-Prescriptive Teaching, involves the assessment of psycholinguistic and perceptual motor abilities that are presumed necessary for learning basic academic skills. Based on the differential pattern of ability strengths and weaknesses resulting from this assessment, individual remedial prescriptions are prescribed. In this article five assumptions underlying this model are identified. Also presented is a comprehensive review of research related to each assumption. The findings seriously challenge the model's validity and suggest that continued advocacy of the model cannot be justified. Children do not appear to profit from current applications of Differential Diagnosis-Prescriptive Teaching. (Author)