An instructional system that is both efficient and effective should present information so that it is easily processed by learners and so that the cognitive structures resulting from instruction correspond to the structure of the content to be learned. This paper presents a discussion of methods for describing content structure and cognitive structure and for comparing the two. Research methods for studying changes in cognitive structure as a result of instruction are presented and illustrated by a number of studies. Finally, implications of structural approaches to cognition and content are examined for the design of instructional systems. (Author)